5) Grass (that is healthy) looks green because
A) it emits green light and absorbs other colors.
B) it absorbs green light and emits other colors.
C) it transmits green light and emits other colors.
D) it reflects green light and absorbs other colors.

D

6) Everything looks red through a red filter because
A) the filter emits red light and absorbs other colors.
B) the filter absorbs red light and emits other colors.
C) the filter transmits red light and absorbs other colors.
D) the filter reflects red light and transmits other colors.

C

7) Which of the following cannot be described by a field?
A) gravitational forces
B) electrical forces
C) magnetic forces
D) radiation pressure

D

8) The frequency of a wave is
A) the number of peaks passing by any point each second.
B) measured in cycles per second.
C) measured in hertz (Hz).
D) equal to the speed of the wave divided by the wavelength of the wave.
E) all of the above

E

9) The wavelength of a wave is
A) how strong the wave is.
B) the distance between a peak of the wave and the next trough.
C) the distance between two adjacent peaks of the wave.
D) the distance between where the wave is emitted and where it is absorbed.
E) equal to the speed of the wave times the wave's frequency.

C

10) How are wavelength, frequency, and energy related for photons of light?
A) Longer wavelength means lower frequency and lower energy.
B) Longer wavelength means higher frequency and lower energy.
C) Longer wavelength means higher frequency and higher energy.
D) Longer wavelength means lower frequency and higher energy.
E) There is no simple relationship because different photons travel at different speeds.

A

11) From lowest energy to highest energy, which of the following correctly orders the different categories of electromagnetic radiation?
A) infrared, visible light, ultraviolet, X rays, gamma rays, radio
B) radio, infrared, visible light, ultraviolet, X rays, gamma rays
C) visible light, infrared, X rays, ultraviolet, gamma rays, radio
D) gamma rays, X rays, visible light, ultraviolet, infrared, radio
E) radio, X rays, visible light, ultraviolet, infrared, gamma rays

B

12) From shortest to longest wavelength, which of the following correctly orders the different categories of electromagnetic radiation?
A) infrared, visible light, ultraviolet, X rays, gamma rays, radio
B) radio, infrared, visible light, ultraviolet, X rays, gamma rays
C) visible light, infrared, X rays, ultraviolet, gamma rays, radio
D) gamma rays, X rays, ultraviolet, visible light, infrared, radio
E) gamma rays, X rays, visible light, ultraviolet, infrared, radio

D

14) Which of the following statements about X rays and radio waves is not true?
A) Neither X rays nor radio waves can penetrate the earth's atmosphere.
B) X rays have shorter wavelengths than radio waves.
C) X rays and radio waves are both forms of light, or electromagnetic radiation.
D) X rays have higher frequency than radio waves.
E) X rays have higher energy than radio waves.

A

15) We can see each other in the classroom right now because we
A) emit thermal radiation.
B) emit visible light.
C) emit infrared light.
D) reflect visible light.
E) reflect infrared light.

D

16) Without telescopes or other aid, we can look up and see the Moon in the night sky because it
A) emits visible light.
B) emits thermal radiation.
C) reflects infrared light.
D) reflects visible light.
E) glows through radioactive decay.

D

17) How many atoms fit across the period at the end of this sentence?
A) hundreds
B) thousands
C) millions
D) billions
E) more than you could count in a lifetime

C

18) What is a compound?
A) a group of molecules
B) a molecule containing hydrogen
C) a molecule containing two or more elements
D) an ionized molecule
E) a molecule containing carbon

C

19) Compared to the volume of its nucleus, the volume of an atom is about
A) the same.
B) a thousand times greater.
C) a million times greater.
D) a billion times greater.
E) a trillion times greater.

E

20) How much electrical charge does an atom with 6 protons, 6 neutrons, and 5 electrons have?
A) a total charge of +17
B) a negative charge of -5
C) a positive charge of +7
D) a positive charge of +1
E) none of the above

D

21) Which of the following statements about electrical charge is true?
A) Two negative charges will attract each other.
B) Two positive charges will attract each other.
C) A positive charge and a negative charge will repel each other.
D) A positive charge and a negative charge will attract each other.

D

26) Each of the following describes an "Atom 1" and an "Atom 2." In which case are the two atoms isotopes of each other?
A) Atom 1: nucleus with 6 protons and 8 neutrons, surrounded by 6 electrons
Atom 2: nucleus with 7 protons and 8 neutrons, surrounded by 7 electrons
B) Atom 1: nucleus with 8 protons and 8 neutrons, surrounded by 8 electrons
Atom 2: nucleus with 8 protons and 8 neutrons, surrounded by 7 electrons
C) Atom 1: nucleus with 92 protons and 143 neutrons, surrounded by 92 electrons
Atom 2: nucleus with 92 protons and 146 neutrons, surrounded by 92 electrons
D) Atom 1: nucleus with 1 proton and 0 neutrons, surrounded by 1 electron
Atom 2: nucleus with 2 protons and 2 neutrons, surrounded by 2 electrons
E) Atom 1: nucleus with 4 protons and 5 neutrons, surrounded by 4 electrons
Atom 2: nucleus with 5 protons and 5 neutrons, surrounded by 4 electrons

C

28) Oxygen has atomic number 8. How many times must an oxygen atom be ionized to create an O+5 ion, and how many electrons will the ion have?
A) It must be ionized three times; it now has five electrons.
B) It must be ionized five times; it now has five electrons.
C) It must be ionized five times; it now has three electrons.
D) It doesn't have to be ionized; it just needs to gain five protons.
E) It doesn't have to be ionized; it already has only three electrons.

C

) At extremely high temperatures (e.g., millions of degrees), which of the following best describes the phase of matter?
A) a gas of rapidly moving molecules
B) a plasma consisting of positively charged ions and free electrons
C) a gas consisting of individual, neutral atoms, but no molecules
D) a plasma consisting of rapidly moving, neutral atoms
E) none of the above (At these extremely high temperatures, matter cannot exist.)

B

30) Sublimation is the process in which
A) molecules go from the solid phase to the liquid phase.
B) molecules go from the liquid phase to the gas phase.
C) molecules go from the solid phase to the gas phase.
D) electrons are stripped from atoms.
E) electrons are captured by ions.

C

31) Dissociation is the process in which
A) the bonds between atoms in a molecule are broken.
B) a molecule goes from the solid phase to the gas phase.
C) the bonds between electrons around an atomic nucleus are broken.
D) an element changes into another form.
E) an electron is shared between atomic nuclei.

A

32) When an atom loses an electron, it becomes
A) sublimated.
B) dissociated.
C) ionized.
D) an isotope.
E) a plasma.

C

33) An atom in an excited state contains more of what type of energy than the same atom in the ground state?
A) mass-energy
B) kinetic energy
C) thermal energy
D) gravitational potential energy
E) electric potential energy

E

34) When an atom absorbs a photon containing energy, any of the following can happen except which?
A) The atom becomes excited.
B) The atom is ionized.
C) An electron moves from an upper energy level to a lower one.
D) An electron moves from a lower energy level to an upper one.

C

35) The loss of an electron from a neutral helium atom results in
A) neutral hydrogen.
B) ionized hydrogen.
C) ionized helium.
D) neutral deuterium.
E) ionized deuterium.

C

36) An electron-volt is
A) the charge of one electron.
B) the energy of one electron.
C) the energy jump between the first and second energy levels of hydrogen.
D) an amount of energy much smaller than a joule.
E) an amount of energy much larger than a joule.

D

37) The study of energy levels in atoms is called
A) special relativity.
B) general relativity.
C) quantum mechanics.
D) classical mechanics.
E) particle physics.

C

38) How can an electron in an atom lose energy to go from a higher energy level to a lower energy level?
A) It loses kinetic energy.
B) It releases a photon equal in energy to its own energy drop.
C) It absorbs a photon equal in energy to its own energy drop.
D) It loses gravitational potential energy.
E) It exchanges gravitational potential energy for kinetic energy.

B

39) If you heat a gas so that collisions are continually bumping electrons to higher energy levels, when the electrons fall back to lower energy levels the gas produces
A) thermal radiation.
B) an absorption line spectrum.
C) an emission line spectrum.
D) X rays.
E) radio waves.

C

40) When an electron in an atom goes from a higher energy state to a lower energy state, the atom
A) emits a photon of a specific frequency.
B) absorbs a photon of a specific frequency.
C) absorbs several photons of a specific frequency.
D) can emit a photon of any frequency.
E) can absorb a photon of any frequency.

A

41) When white light passes through a cool cloud of gas, we see
A) visible light.
B) infrared light.
C) thermal radiation.
D) an absorption line spectrum.
E) an emission line spectrum.

D

42) Spectra from neutral atoms compared with spectra from ionized atoms of the same element
A) are the same.
B) are slightly redshifted.
C) are slightly blueshifted.
D) have different sets of spectral lines.
E) have the same sets of spectral lines but different widths for those lines.

D

43) Which of the following objects is not a close approximation of a thermal emitter?
A) hot, thin gas
B) a star
C) a filament in a light bulb
D) you
E) a planet

A

44) Thermal radiation is defined as
A) radiation produced by a hot object.
B) radiation in the infrared part of the spectrum.
C) radiation that depends only on the emitting object's temperature.
D) radiation in the form of emission lines from an object.
E) radiation that is felt as heat.

C

45) A perfectly opaque object that absorbs all radiation and reemits the absorbed energy as thermal radiation is
A) a hot, dense cloud of gas.
B) a cold, dense cloud of gas.
C) an infrared radiation emitter.
D) a thermal emitter.
E) transparent.

D

47) Which of the following statements about thermal radiation is always true?
A) A hot object emits photons with a longer wavelength than a cool object.
B) A hot object emits photons with a higher average energy than a cool object.
C) A hot object emits more radio waves than a cool object.
D) A hot object emits more X rays than a cool object.

B

48) If two objects are the same size but one object is 3 times hotter than the other object, the hotter object emits
A) 3 times more energy.
B) 9 times more energy.
C) 12 times more energy.
D) 81 times more energy.
E) none of the above

D

49) A gas heated to millions of degrees would emit
A) mostly radio waves.
B) mostly X rays.
C) mostly ultraviolet light.
D) an equal amount of all wavelengths of light.
E) no light, because it is too hot.

B

51) The spectra of most galaxies show redshifts. This means that their spectral lines
A) always are in the red part of the visible spectrum.
B) have wavelengths that are longer than normal.
C) have wavelengths that are shorter than normal.
D) have a higher intensity in the red part of the spectrum.
E) have normal wavelengths, but absorption of light makes them appear red.

B

53) From laboratory measurements, we know that a particular spectral line formed by hydrogen appears at a wavelength of 121.6 nanometers (nm). The spectrum of a particular star shows the same hydrogen line appearing at a wavelength of 121.8 nm. What can we conclude?
A) The star is moving toward us.
B) The star is moving away from us.
C) The star is getting hotter.
D) The star is getting colder.
E) The "star" actually is a planet.

B

54) How does the spectrum of a molecule differ from the spectrum of an atom?
A) A molecule does not have spectral lines due to electrons changing energy levels.
B) A molecule has additional spectral lines due to changes in its rotational and vibrational energies.
C) Molecules only have spectral lines at ultraviolet wavelengths.
D) Most atoms only have spectral lines at infrared wavelengths.
E) An atom has a wider range of spectral lines than molecules.

B

55) You observe a distant galaxy. You find that a spectral line normally found in the visible part of the spectrum is shifted toward the infrared. What do you conclude?
A) The galaxy is moving away from you.
B) The galaxy is moving toward you.
C) The galaxy has very weak gravity.
D) The galaxy is made purely of hydrogen.
E) The composition of the galaxy is changing.

A

56) If one object has a large redshift and another object has a small redshift, what can we conclude about these two objects?
A) The one with the large redshift is moving toward us faster than the one with the small redshift.
B) The one with the large redshift is moving away from us, and the one with the small redshift is moving toward us.
C) The one with the large redshift is moving away from us faster than the one with the small redshift.
D) The one with the large redshift is hotter and therefore is putting out more radiation.
E) The one with the large redshift is redder than the other one.

C

57) If we observe one edge of a planet to be redshifted and the opposite edge to be blueshifted, what can we conclude about the planet?
A) The planet is actually two bodies, one moving toward us, the other away from us.
B) The planet is in the process of falling apart.
C) The planet is in the process of formation.
D) The planet is rotating.
E) The planet's surface is very different from one side to the other.

D

58) Suppose you see two stars: a blue star and a red star. Which of the following can you conclude about the two stars? Assume that no Doppler shifts are involved. (Hint: Think about the laws of thermal radiation.)
A) The red star is more massive than the blue star.
B) The blue star is more massive than the red star.
C) The blue star is farther away than the red star.
D) The blue star has a hotter surface temperature than the red star.
E) The red star has a hotter surface temperature than the blue star.

D

59) You observe the same spectral line in two stars that are identical in every way except that one rotates faster than the other. How does the spectral line differ between the two?
A) There is no difference.
B) The line in the faster rotating star is blueshifted.
C) The line in the faster rotating star is redshifted.
D) The line in the faster rotating star is broader.
E) The line in the faster rotating star is narrower.

D

) Energy and power are different words for the same thing.

Answer: FALSE

) Process of Science: I am doing science when I already know the answer to my scientific question and I am searching for evidence in the natural world strictly to support what I know.

Answer: FALSE

Grass is green because it absorbs green light, reflecting all other colors.

Answer: FALSE

The shorter the wavelength of light, the higher its frequency.

Answer: TRUE

The greater the wavelength of light, the greater its energy.

Answer: FALSE

X rays, because they have more energy, travel through space faster than visible light.

Answer: FALSE

X rays are always more intense than radio waves.

Answer: FALSE

8) You are currently emitting electromagnetic waves.

Answer: TRUE

There are more atoms in a glass of water than stars in the observable universe.

Answer: TRUE

Atomic nuclei consist of protons and electrons.

Answer: FALSE

) Electrons orbit an atomic nucleus like planets orbit the Sun.

Answer: FALSE

12) The atomic nuclei of the same element always have the same number of protons.

Answer: TRUE

13) The atomic nuclei of the same element always have the same number of neutrons.

Answer: FALSE

The energy levels for electrons vary from one element to another.

Answer: TRUE

The energy levels of an element and its ion are the same.

Answer: FALSE

Lines of a particular element appear at the same wavelength in both emission and absorption line spectra.

Answer: TRUE

Any object moving relative to Earth will have a Doppler shift.

Answer: FALSE

Emission lines from different ionization states of the same element appear in the same place in the spectrum.

Answer: FALSE

1) What is the difference between energy and power?
A) Power is the rate at which energy is used, so its units are a unit of energy divided by a unit of time.
B) Power is measured in joules and energy is measured in watts.
C) Power is used to describe energy of light, while the term energy has a broader meaning.
D) There's no difference: Energy and power are different names for the same thing.

A

Visible light from a distant star can be spread into a spectrum by using a glass prism or
A) a diffraction grating.
B) adaptive optics.
C) a telescope.
D) a flat glass mirror.

A

3) Suppose you watch a leaf bobbing up and down as ripples pass it by in a pond. You notice that it does two full up and down bobs each second. Which statement is true of the ripples on the pond?
A) They have a frequency of 4 hertz.
B) They have a frequency of 2 hertz.
C) We can calculate the wavelength of the ripples from their frequency.
D) They have a wavelength of two cycles per second.

B

4) Suppose you know the frequency of a photon and the speed of light. What else can you determine about the photon?
A) its temperature
B) its acceleration
C) its wavelength and energy
D) the chemical composition of the object that emitted it

C

5) When considering light as made up of individual "pieces," each characterized by a particular amount of energy, the pieces are called
A) photons.
B) wavicles.
C) gamma rays.
D) frequencies.

A

7) Which forms of light are lower in energy and frequency than the light that our eyes can see?
A) infrared and radio
B) ultraviolet and X rays
C) visible light
D) infrared and ultraviolet

A

8) If we say that a material is opaque to ultraviolet light, we mean that it
A) absorbs ultraviolet light.
B) emits ultraviolet light.
C) transmits ultraviolet light.
D) reflects ultraviolet light.

A

9) Suppose you built a scale-model atom in which the nucleus is the size of a tennis ball. About how far would the cloud of electrons extend?
A) a few meters
B) several centimeters
C) several kilometers
D) to the Sun

C

10) Which of the following best describes the fundamental difference between two different chemical elements (such as oxygen and carbon)?
A) They have different atomic mass numbers.
B) They have different numbers of protons in their nucleus.
C) They have different numbers of electrons.
D) They have different names.

B

12) An atom which has 4 protons and 6 neutrons will be electrically neutral if it contains
A) 4 electrons.
B) 6 electrons.
C) 10 electrons.
D) at least one electron.

A

14) Which of the following transitions within an atom is not possible?
A) An electron begins in an excited state and then gains enough energy to jump to the ground state.
B) An electron begins in the ground state and then gains enough energy to jump to an excited state.
C) An electron begins in the ground state and then gains enough energy to become ionized.
D) An electron begins in an excited state and then gains enough energy to become ionized.

A

15) An atom that has fewer electrons than protons is called a/an
A) molecule.
B) solid.
C) ion.
D) plasma.

C

16) Suppose you look at a spectrum of visible light by looking through a prism or diffraction grating. How can you decide whether it is an emission line spectrum or an absorption line spectrum?
A) An emission line spectrum consists of bright lines on a dark background, while an absorption line spectrum consists of dark lines on a rainbow background.
B) An emission line spectrum consists of a long bright line, while an absorption line spectrum consists of a long dark line.
C) The only way to decide is to make a graph of the intensity of the light at every wavelength, and then analyze the graph carefully.
D) The emission line spectrum is produced by electrons jumping up in energy level, while the absorption line spectrum is produced by electrons jumping down in energy level.

A

18) According to the laws of thermal radiation, hotter objects emit photons with
A) a lower average frequency.
B) a shorter average wavelength.
C) a lower average energy.
D) a higher average speed.

B

19) Suppose you want to know the chemical composition of a distant star. Which piece of information is most useful to you?
A) The peak energy of the star's thermal radiation.
B) The Doppler shift of the star's spectrum.
C) The wavelengths of spectral lines in the star's spectrum.
D) Whether the star's spectrum has more emission lines or more absorption lines.

C

21) You observe a distant galaxy. You find that a spectral line of hydrogen that is shifted from its normal location in the visible part of the spectrum into the infrared part of the spectrum. What can you conclude?
A) The galaxy is moving away from you.
B) The galaxy is moving towards you.
C) The galaxy has very weak gravity.
D) The galaxy is made purely of hydrogen.

A

Suppose you are listening to a radio station that broadcasts at a frequency of 97 Mhz (megahertz). Which of the following statements is true?
A) The radio waves from the radio station are causing electrons in your radio's antenna to move up and down 97 million times each second.
B) The radio waves from the radio station have a wavelength of 97 million meters.
C) The "radio waves" received by your radio are not light waves like those we talk about in astronomy, but rather are a special type of sound wave.
D) The radio station broadcasts its signal with a power of 97 million watts.

A

4) Gamma rays have a very small
A) energy.
B) frequency.
C) mass.
D) wavelength.

D

5) Suppose a photon has a frequency of 300 million hertz (300 megahertz). What is its wavelength?
A) 1 meter
B) 1/300,000 meter
C) 300 million meters
D) A photon's wavelength cannot be determined from its frequency.

A

6) Which of the following best describes why we say that light is an electromagnetic wave?
A) Light can be produced only by electric or magnetic appliances.
B) Light is produced only when massive fields of electric and magnetic energy collide with one another.
C) The passage of a light wave can cause electrically charged particles to move up and down.
D) The term electromagnetic wave arose for historical reasons, but we now know that light has nothing to do with either electricity or magnetism.

C

7) Which of the following statements about X rays and radio waves is not true?
A) X rays travel through space faster than radio waves.
B) X rays have shorter wavelengths than radio waves.
C) X rays and radio waves are both forms of light, or electromagnetic radiation.
D) X rays have higher frequency than radio waves.

A

8) Each of the following describes an "Atom 1" and an "Atom 2." In which case are the two atoms different isotopes of the same element?
A) Atom 1: nucleus with 6 protons and 8 neutrons, surrounded by 6 electrons;
Atom 2: nucleus with 7 protons and 8 neutrons, surrounded by 7 electrons.
B) Atom 1: nucleus with 7 protons and 8 neutrons, surrounded by 7 electrons;
Atom 2: nucleus with 7 protons and 7 neutrons, surrounded by 7 electrons.
C) Atom 1: nucleus with 8 protons and 8 neutrons, surrounded by 8 electrons;
Atom 2: nucleus with 8 protons and 8 neutrons, surrounded by 7 electrons.
D) Atom 1: nucleus with 4 protons and 5 neutrons, surrounded by 4 electrons;
Atom 2: nucleus with 5 protons and 5 neutrons, surrounded by 4 electrons.

B

9) Suppose you had molecular oxygen (O2) chilled enough so that it was in liquid form. Which of the following best describes the phase changes that would occur as you heated the liquid oxygen to high temperature?
A) It would evaporate into a gas, then the molecules would dissociate into individual oxygen atoms, then the atoms would become increasingly ionized as you continued to raise the temperature.
B) The liquid molecules would quickly dissociate into a liquid of individual oxygen atoms. These atoms would then evaporate into a gas, and then become ionized to make a plasma.
C) It would sublimate into a gas, then the molecules would lose electrons until no electrons were left, then the molecules would dissociate into individual oxygen nuclei.
D) The cold temperature would first cause the oxygen to solidify. The solid would then sublimate into a gas, which would then become a plasma as the molecules lost their electrons, until finally it consisted of bonded pairs of oxygen nuclei stripped bare of any electrons.

A

10) Consider an atom of oxygen in which the nucleus contains 8 protons and 8 neutrons. If it is doubly ionized, what is the charge of the oxygen ion and how many electrons remain in the ion?
A) Charge = +2; number of remaining electrons = 8.
B) Charge = -2; number of remaining electrons = 10.
C) Charge = +2; number of remaining electrons = 6.
D) Charge = +2; number of remaining electrons = 2.

C

11) Which of the following statements about electrons is not true?
A) Electrons orbit the nucleus rather like planets orbiting the Sun.
B) Within an atom, an electron can have only particular energies.
C) An electron has a negative electrical charge.
D) Electrons have very little mass compared to protons or neutrons.
E) Electrons can jump between energy levels in an atom only if they receive or give up an amount of energy equal to the difference in energy between the energy levels.

A

12) Which of the following conditions lead you to see an absorption line spectrum from a cloud of gas in interstellar space?
A) The cloud is extremely hot.
B) The cloud is visible primarily because it reflects light from nearby stars.
C) The cloud is cool and very dense, so that you cannot see any objects that lie behind it.
D) The cloud is cool and lies between you and a hot star.

D

13) No object produces a perfect thermal radiation spectrum, but many objects produce close approximations. Which of the following would not produce a close approximation to a thermal radiation spectrum?
A) a hot, thin (low-density, nearly transparent) gas
B) a filament in a standard (incandescent) light bulb
C) a star
D) you

A

14) Which of the following statements about thermal radiation is always true?
A) A hot object emits more radiation per unit surface area than a cool object.
B) A cold object produces more total infrared and radio emission per unit surface area than a hot object.
C) A hot object produces more total infrared emission than a cooler object.
D) All the light emitted by hot object has higher energy than the light emitted by a cooler object.

A

15) Betelgeuse is the bright red star representing the left shoulder of the constellation Orion. All the following statements about Betelgeuse are true. Which one can you infer from its red color?
A) It is much brighter than the Sun.
B) Its surface is cooler than the surface of the Sun.
C) It is much more massive than the Sun.
D) It is moving away from us.

B

16) The planet Neptune is blue in color. How would you expect the spectrum of visible light from Neptune to be different from the visible-light spectrum of the Sun?
A) The two spectra would have similar shapes, except Neptune's spectrum would be missing a big chunk of the red light that is present in the Sun's spectrum.
B) The two spectra would have similar shapes, except Neptune's spectrum would be missing a big chunk of the blue light that is present in the Sun's spectrum.
C) Neptune's spectrum would peak at a much longer wavelength than the Sun's spectrum.
D) There is no way to predict the answer to this question, since planets and stars are made of such different things.

A

17) All of the following statements about the Sun's corona are true. Which one explains why it is a source of X rays?
A) The temperature of the corona's gas is some 1 to 2 million Kelvin.
B) The corona lies above the visible surface of the Sun.
C) The corona's gas consists mostly of hydrogen and helium.
D) The corona's structure is largely shaped by magnetic fields.

A

18) Laboratory measurements show hydrogen produces a spectral line at a wavelength of 486.1 nanometers (nm). A particular star's spectrum shows the same hydrogen line at a wavelength of 486.0 nm. What can we conclude?
A) The star is moving away from us.
B) The star is getting hotter.
C) The star is moving toward us.
D) The star is getting colder.

C

19) Suppose that Star X and Star Y both have redshifts, but Star X has a larger redshift than Star Y. What can you conclude?
A) Star X is moving away from us faster than Star Y.
B) Star Y is moving away from us faster than Star X.
C) Star X is hotter than Star Y.
D) Star X is moving away from us and Star Y is moving toward us.

A

20) If we observe one edge of a planet to be redshifted and the opposite edge to be blueshifted, what can we conclude about the planet?
A) We must actually be observing moons orbiting the planet in opposite directions, not the planet itself.
B) The planet is rotating.
C) The planet is in the process of falling apart.
D) The planet is in the process of formation.

B

21) Studying a spectrum from a star can tell us a lot. All of the following statements are true except one. Which statement is not true?
A) The total amount of light in the spectrum tells us the star's radius.
B) The peak of the star's thermal emission tells us its temperature: hotter stars peak at shorter (bluer) wavelengths.
C) We can identify chemical elements present in the star by recognizing patterns of spectral lines that correspond to particular chemicals.
D) Shifts in the wavelengths of spectral lines compared to the wavelengths of those same lines measured in a laboratory on Earth can tell us the star's speed toward or away from us.

A

22) Suppose that two stars are identical in every way—for example, same distance, same mass, same temperature, same chemical composition, and same speed relative to Earth—except that one star rotates faster than the other. Spectroscopically, how could you tell the stars apart?
A) The faster rotating star has wider spectral lines than the slower rotating star.
B) The faster rotating star will have an emission line spectrum while the slower rotating star will have an absorption line spectrum.
C) The peak of thermal emission will be at a shorter wavelength for the faster rotating star than for the slower rotating star.
D) There is no way to tell the stars apart spectroscopically, because their spectra will be identical.

A

1) Which of the following statements about light focusing is not true?
A) In a healthy eye, light is focused on the retina.
B) Film should be placed at the focal plane in a camera.
C) If you try to look at an image that is not formed at the focal plane, it will be blurry.
D) The focal plane of a reflecting telescope is always located within a few inches of the primary mirror.

D

2) Suppose the angular separation of two stars is smaller than the angular resolution of your eyes. How will the stars appear to your eyes?
A) You will not be able to see these two stars at all.
B) The two stars will look like a single point of light.
C) The two stars will appear to be touching, looking rather like a small dumbbell.
D) You will see two distinct stars.
E) You will see only the larger of the two stars, not the smaller one.

B

3) Which of the following is a principal advantage of CCDs over photographic film?
A) CCDs allow long exposures (e.g., minutes or hours), and film does not.
B) CCDs can record the colors of astronomical objects accurately, while film cannot.
C) CCDs capture a much higher percentage of the incoming photons than does film.
D) Images recorded with CCDs never require any image processing, while images recorded by film often do.
E) CCDs can be attached to modern telescopes more easily than cameras.

C

4) Order the following in order of increasing efficiency of detecting photons of visible light.
A) eye, photographic film, CCD
B) photographic film, CCD, eye
C) CCD, eye, photographic film
D) CCD, photographic film, eye
E) eye, CCD, photographic film

A

5) Which of the following statements best describes the two principal advantages of telescopes over eyes?
A) Telescopes can collect far more light with far better angular resolution.
B) Telescopes can collect far more light with far greater magnification.
C) Telescopes have much more magnification and better angular resolution.
D) Telescopes collect more light and are unaffected by twinkling.
E) Telescopes can see farther without image distortion and can record more accurate colors.

A

6) Currently, the largest optical telescope mirrors have a diameter of
A) 1 m.
B) 2 m.
C) 5 m.
D) 10 m.
E) 100 m.

D

8) Which of the following could not be measured by an observation that uses only imaging?
A) the rate at which a variable star brightens and dims
B) the general shape of an interstellar cloud of gas
C) the color of a planet
D) the brightness of a star in our sky
E) the number of bright stars in a nearby star cluster

A

9) Which of the following could not be determined by an observation that uses only spectroscopy?
A) the chemical composition of a distant star
B) the speed at which a distant galaxy is moving away from us
C) the surface temperature of a distant star
D) the rotation rate of a distant star
E) the size of a distant galaxy

E

10) What is meant by spectral resolution?
A) It is a measure of how much energy an object emits in different parts of the electromagnetic spectrum.
B) It is a measure of how close two spectral lines can be distinguished.
C) It is a measure of how close two point sources can be distinguished.
D) It is the same as angular resolution when applied to telescopes operating at different wavelengths.

B

11) Which of the following studies is best suited to a time monitoring experiment?
A) studying how different stars differ in their chemical compositions
B) studying whether a particular star's brightness is steady or variable
C) determining the age of the solar system
D) measuring the rotation rate of a distant star
E) estimating the time since the Big Bang

B

12) Which of the following is always true about images captured with X-ray telescopes?
A) They are always very pretty.
B) They are always displayed with the highest possible angular resolution.
C) They are always useful for seeing through things.
D) They are always displayed in false color.
E) They are always displayed with north pointing upward in the images.

D

13) What do astronomers mean by light pollution?
A) Light pollution refers to pollution caused by light industry as opposed to heavy industry.
B) Light pollution refers to harmful gases emitted by common street lights.
C) Light pollution refers to light used for human activities that brightens the sky and hinders astronomical observations.
D) Light pollution refers to the lights that must be used inside major observatories and that make it difficult for astronomers' eyes to adapt to darkness.
E) Light pollution is another name for sunlight, which makes it impossible to see stars in the daytime.

C

14) What causes stars to twinkle?
A) It is intrinsic to the stars–their brightness varies as they expand and contract.
B) variations in the absorption of the atmosphere
C) variable absorption by interstellar gas along the line of sight to the star
D) bending of light rays by turbulent layers in the atmosphere
E) the inability of the human eye to see faint objects

D

15) What is the purpose of adaptive optics?
A) to improve the angular resolution of telescopes in space
B) to eliminate the distorting effects of atmospheric turbulence for telescopes on the ground
C) to increase the collecting area of telescopes on the ground
D) to increase the magnification of telescopes on the ground
E) to allow several small telescopes to work together like a single larger telescope

B

16) What is an artificial star?
A) a point of light in Earth's atmosphere created by a laser for the purpose of monitoring atmospheric fluctuations
B) a satellite orbiting Earth
C) a meteor
D) a possible source of dark matter in the universe
E) the unseen member of a binary star system

A

17) Which of the following is not a good reason to place observatories on remote mountain tops?
A) to reduce light pollution
B) to reduce light distortion
C) to reduce light absorption
D) to be able to observe at radio wavelengths
E) to be able to observe at infrared wavelengths

D

18) Why do astronomers need different telescope designs to observe across the electromagnetic spectrum?
A) New telescopes incorporate new technology to increase their efficiency.
B) Telescopes have to adapt to the greater distortion of the atmosphere at shorter wavelengths.
C) Photons of different energy behave differently and require different collection strategies.
D) Light pollution is worse at radio wavelengths than visible wavelengths.
E) Astronomers and engineers enjoy the challenge of making new

C

21) Telescopes operating at this wavelength must be cooled to observe faint astronomical objects.
A) radio
B) extreme infrared
C) visible
D) X-ray
E) gamma-ray

B

22) At which wavelength range is there no current or planned space observatory?
A) radio
B) infrared
C) visible
D) X-ray
E) gamma-ray

A

23) In what part of the electromagnetic spectrum do the biggest telescopes on Earth operate?
A) radio
B) infrared
C) visible
D) ultraviolet
E) X-ray

A

24) What does the technique of interferometry allow?
A) It allows two or more telescopes to obtain a total light-collecting area much larger than the total light-collecting area of the individual telescopes.
B) It allows two or more telescopes to obtain the angular resolution of a single telescope much larger than any of the individual telescopes.
C) It allows us to determine the chemical composition of stars.
D) It allows astronomers to make astronomical observations without interference from light pollution.
E) It allows the same telescope to make images with both radio waves and visible light.

B

25) The largest effective telescope, created by radio interferometry, is the size of
A) several football fields, in a natural depression in Puerto Rico.
B) tens of miles across, in the deserts of New Mexico.
C) the state of New Mexico.
D) the continental United States.
E) Earth.

E

26) In what wavelength range was interferometry first routinely used?
A) radio
B) infrared
C) optical
D) ultraviolet
E) X-ray

A

The lens in your eye forms an upside-down image of the world.

Answer: TRUE

) A radio telescope and an optical telescope of the same size have the same angular resolution.

Answer: FALSE

The angular resolution of a telescope is never less than its diffraction limit.

Answer: TRUE

Professional astronomical telescopes generally have a much greater magnification than the telescopes you can buy in stores.

Answer: FALSE

A larger telescope will always have a higher spectral resolution than a smaller telescope when observing at the same wavelength.

Answer: FALSE

Most astronomical objects emit light over a broad range of wavelengths.

Answer: TRUE

Improvements in technology will eventually allow the entire electromagnetic spectrum to be observed from high mountaintop observatories.

Answer: FALSE

X rays from astronomical objects can only be detected from telescopes in space.

Answer: TRUE

X-ray telescope mirrors are very similar to optical telescope mirrors.

Answer: FALSE

) The Hubble Space Telescope is famous because, at least at the time of its launch, it was the largest visible light telescope ever built.

Answer: FALSE

Process of Science: If any single test of a scientific hypothesis contradicts it, the hypothesis must be revised.

Answer: TRUE

1) Which of the following best describes what we mean by the focal plane of a telescope?
A) It is the upper surface of the telescope's primary lens or mirror.
B) It is the place where, if we mounted film or an electronic detector, we could get a clear (not blurry) image of an object viewed through the telescope.
C) It is the lower surface of the telescope's primary lens or mirror.
D) It is the surface of the lens on the eyepiece, through which you would look to see objects in the telescope's field of view.

B

) What does angular resolution measure?
A) the angular size of the smallest features that the telescope can see
B) the brightness of an image
C) the size of an image
D) the number of electromagnetic waves captured by an image

A

3) What is the angular resolution of the human eye?
A) about 1 degree
B) about 1 arcsecond (1/3600 of a degree)
C) about 1 arcminute, or 1/60 of a degree
D) about 1 milliarcsecond

C

4) What is a CCD?
A) It is an electronic detector that can be used in place of photographic film for making images.
B) It is an abbreviation for the world's largest operating telescope.
C) It refers to any kind of instrument that can be hooked up to a telescope.
D) It is a unit used by astronomers to measure angular resolution.

A

6) Which of the following statements best describes the difference between a refracting telescope and a reflecting telescope?
A) A refracting telescope uses a transparent glass lens to focus light while a reflecting telescope uses a mirror to focus light.
B) A refracting telescope produces refracted images while a reflecting telescope produces reflected images.
C) Reflecting telescopes make much clearer images than can refracting telescopes of the same size.
D) It is much easier to make a large refracting telescope than a large reflecting telescope.

A

) What do we mean by the diffraction limit of a telescope?
A) It describes the farthest distance to which the telescope can see.
B) It is the angular resolution the telescope could achieve if nothing besides the size of its light-collecting area affected the quality of its images.
C) It is the maximum size to which any telescope can be built.
D) It describes the maximum exposure time for images captured with the telescope.

B

8) Which of the following is not one of the three main categories of observation generally used by astronomers?
A) filtering to look at just a single color from an object
B) timing to track how an object's brightness varies with time
C) spectroscopy to spread an object's light into a spectrum
D) imaging to get a picture of an astronomical objects

A

9) Suppose you want to determine the chemical composition of a distant planet or star. Which of the following will be most useful to have?
A) high angular resolution
B) high turbulence
C) a radio telescope
D) high spectral resolution

D

14) Which of the following wavelength regions can be studied with telescopes on the ground?
A) radio, visible, and very limited portions of the infrared and ultraviolet regions
B) all light with wavelengths longer than ultraviolet wavelengths
C) all light with wavelengths shorter than infrared wavelengths
D) infrared, visible, and ultraviolet light

A

1) Suppose you have two small photographs of the Moon. Although both look the same at small size, when you blow them up to poster size one of them still looks sharp while the other one becomes fuzzy (grainy) looking. Which of the following statements is true?
A) The one that still looks sharp at large size has better (smaller) angular resolution than the one that looks fuzzy.
B) The one that looks fuzzy at large size has better angular resolution (smaller) than the one that looks sharp.
C) Both photographs have the same angular resolution, because they were both printed at the same sizes in each case.
D) Both photographs have the same angular resolution, because they are both photographs of the same object.

A

2) The angular separation of two stars is 0.1 arcseconds and you photograph them with a telescope that has an angular resolution of 1 arcsecond. What will you see?
A) The two stars will appear to be touching, looking rather like a small dumbbell.
B) The stars will not show up at all in your photograph.
C) The photo will seem to show only one star rather than two.
D) You will see two distinct stars in your photograph.

C

3) Suppose you point your telescope at a distant object. Which of the following is not an advantage of taking a photograph of the object through the telescope as compared to just looking at the object through the telescope?
A) The photograph will have far better angular resolution than you can see with your eye.
B) By using a long exposure time, the photograph can allow you to see objects that would be too dim to see with your eye.
C) If taken with a camera with a sensitive detector such as a CCD, the photograph can capture a much larger percentage of the incoming photons than can your eye.
D) The photograph provides a more reliable record of what is seen through the telescope than can a drawing made by eye.

A

4) Which of the following best describes the principle advantage of CCDs over photographic film?
A) CCDs allow long exposures (e.g., minutes or hours) and film does not.
B) CCDs capture a much higher percentage of the incoming photons than film.
C) CCDs can record the colors of astronomical objects accurately while film cannot.
D) CCDs can be attached to modern telescopes more easily than can photographic film.

B

5) How does the light-collecting area of an 8-meter telescope compare to that of a 2-meter telescope?
A) The 8-meter telescope has 16 times the light-collecting area of the 2-meter telescope.
B) The 8-meter telescope has 4 times the light-collecting area of the 2-meter telescope.
C) The 8-meter telescope has 8 times the light-collecting area of the 2-meter telescope.
D) The answer cannot be determined from the information given in the question.

A

6) Which of the following best describes the development of astronomical telescopes over the past 60 years?
A) Over the 60-year period, telescopes have gradually gotten bigger and more powerful.
B) Although there have been advances in cameras and computing power, telescopes themselves have not changed much in the last 60 years.
C) The world's most powerful telescope remained the same for most of this period, but in the past 20 years many new and more powerful telescopes have been built.
D) The only major change in telescope power has occurred because of our ability to launch telescopes into space rather than operating them only from the ground.

C

7) Which of the following best describes why radio telescopes are generally much larger in size than telescopes designed to collect visible light?
A) Getting an image of the same angular resolution requires a much larger telescope for radio waves than for visible light.
B) Radio telescopes are designed to collect sound rather than light.
C) It is because radio telescopes are used in the daytime and visible light telescopes are used at night.
D) Objects that emit radio waves are always much larger than objects that emit visible light, and therefore require larger telescopes.

A

8) Which of the following studies is best suited to astronomical observations that fall into the category called timing?
A) studying how different planets differ in their surface compositions
B) studying how a star's brightness varies over a period of 3 years
C) measuring the rotation rate of a distant star
D) determining the age of the solar system

B

9) Which of the following is not a reason why telescopes tend to be built on mountaintops that are relatively far from cities and are in regions with dry climates?
A) The thin air on mountaintops makes the glass in telescope mirrors less susceptible to warping.
B) Being on a high mountain top means being relatively high in the atmosphere, which tends to limit turbulence.
C) Dry regions mean less rain and clouds, and mountaintops in dry regions may even allow some infrared observations.
D) Mountaintops far from cities are generally subject to less light pollution than locations nearer to cities.

A

11) Which of the following is not an advantage of the Hubble Space Telescope over ground-based telescopes?
A) It is closer to the stars.
B) Stars do not twinkle when observed from space.
C) It can observe infrared and ultraviolet light, as well as visible light.
D) It never has to close because of cloudy skies.

A

12) The Chandra X-Ray Observatory must operate in space because
A) X rays are too dangerous to be allowed on the ground.
B) X rays do not penetrate Earth's atmosphere.
C) X-ray telescopes require the use of grazing incidence mirrors.
D) It was built by NASA.

B

13) Which of the following telescopes would benefit most from adaptive optics?
A) The Keck I Telescope on Mauna Kea.
B) The Hubble Space Telescope.
C) The Arecibo Radio Telescope in Puerto Rico.
D) The Chandra X-Ray Observatory.

A

14) Consider two future observatories in space. Observatory X consists of a single 50-meter telescope. Observatory Y is an interferometer consisting of five 10-meter telescopes, spread out over a region 100 meters across. Which observatory can detect dimmer stars, and which one can see more detail in its images? (Assume all else is equal, such as quality of optics, types of instruments, and so on.)
A) Observatory X can detect dimmer stars and Observatory Y reveals more detail in images.
B) Observatory Y can detect dimmer stars and Observatory X reveals more detail in images.
C) Observatory X both detects dimmer stars and reveals more detail in images.
D) Observatory Y both detects dimmer stars and reveals more detail in images.

A

15) Which of the following is not a major reason why astronomers would like an observatory on the far side of the Moon?
A) Telescopes on the Moon could see objects in all parts of the sky equally well, whereas telescopes on Earth can see only portions of the sky that depend on their latitude.
B) Radio astronomy would be advantageous on the Moon because human radio transmissions are less likely to cause interference, especially on the far side of the Moon.
C) It would be possible to put telescopes for ultraviolet and X-ray astronomy on the surface, unlike the case on the surface of the Earth.
D) Telescopes on the Moon could observe stars even when it is daytime on the Moon.

A

1) In the late 1800s, Kelvin and Helmholtz suggested that the Sun stayed hot thanks to gravitational contraction. What was the major drawback of this idea?
A) It predicted that the Sun could last only about 25 million years, which is far less than the age of Earth.
B) It predicted that the Sun would shrink noticeably as we watched it, and the Sun appears to be stable in size.
C) It is physically impossible to generate heat simply by making a star shrink in size.
D) It predicted that Earth would also shrink, which would make it impossible to have stable geology on our planet.
E) It was proposed before Einstein's theory of general relativity and was therefore incorrect.

A

5) What is the Sun made of?
A) 100 percent hydrogen and helium
B) 50 percent hydrogen, 25 percent helium, 25 percent other elements
C) 70 percent helium, 28 percent hydrogen, 2 percent other elements
D) 70 percent hydrogen, 28 percent helium, 2 percent other elements
E) 98 percent hydrogen, 2 percent helium and other elements

D

6) The phase of matter in the Sun is
A) gas.
B) plasma.
C) liquid.
D) solid.
E) a mixture of all of the above

B

7) What are the appropriate units for the Sun's luminosity?
A) watts
B) joules
C) meters
D) Newtons
E) kilograms

A

8) What is the average temperature of the surface of the Sun?
A) 1 million K
B) 100,000 K
C) 10,000 K
D) 6,000 K
E) 1,000 K

D

9) Which is closest to the temperature of the core of the Sun?
A) 10,000 K
B) 100,000 K
C) 1 million K
D) 10 million K
E) 100 million K

D, or it could be 15 million K be prepared for both

11) Which layer of the Sun do we normally see?
A) photosphere
B) corona
C) chromosphere
D) convection zone
E) radiation zone

A

12) The core of the Sun is
A) at the same temperature and density as the surface.
B) at the same temperature but denser than the surface.
C) hotter and denser than the surface.
D) constantly rising to the surface through convection.
E) composed of iron.

C

13) Based on its surface temperature of 5,800 K, what color are most of the photons that leave the Sun's surface?
A) blue
B) red
C) yellow
D) orange
E) green

E

15) Sunspots are cooler than the surrounding solar surface because
A) they are regions where convection carries cooler material downward.
B) strong magnetic fields slow convection and prevent hot plasma from entering the region.
C) magnetic fields trap ionized gases that absorb light.
D) there is less fusion occurring there.
E) magnetic fields lift material from the surface of the Sun, cooling off the material faster.

B

18) Hydrogen fusion in the Sun requires a temperature (in Kelvin) of
A) thousands of degrees.
B) millions of degrees.
C) billions of degrees.
D) trillions of degrees.
E) any temperature, as long as gravity is strong enough.

B

19) At the center of the Sun, fusion converts hydrogen into
A) hydrogen compounds.
B) plasma.
C) radiation and elements like carbon and nitrogen.
D) radioactive elements like uranium and plutonium.
E) helium, energy, and neutrinos.

E

20) How much mass does the Sun lose through nuclear fusion per second?
A) 4 tons
B) 4 million tons
C) 600 tons
D) 600 million tons
E) Nothing: mass is conserved.

B

) Suppose you put two protons near each other. Because of the electromagnetic force, the two protons will
A) collide.
B) remain stationary.
C) attract each other.
D) repel each other.
E) join together to form a nucleus.

D

22) Which is the strongest of the fundamental forces in the universe?
A) strong force
B) weak force
C) electromagnetic force
D) gravitational force
E) none of the above

A

23) The first step in the proton-proton chain produces an antielectron, or positron. What happens to the positron?
A) It slowly works its way to the Sun's surface, where it escapes into space.
B) It rapidly escapes from the Sun, traveling into space at nearly the speed of light.
C) It is rapidly converted to energy when it meets an ordinary electron, resulting in matter-antimatter annihilation.
D) It quickly meets an ordinary electron, forming an electron-positron pair that remains stable.
E) It joins with a nearby neutron to form a proton.

C

24) The overall fusion reaction by which the Sun currently produces energy is
A) 3 H ⇒ 1 Li + energy.
B) 3 He ⇒ 1 C + energy.
C) 4 H ⇒ 4 He + energy.
D) 6 H ⇒ 1 He + energy.
E) 4 H ⇒ 1 He + energy.

E

25) Why must the Sun's rate of fusion gradually rise over billions of years?
A) The Sun becomes less efficient and must increase the rate of fusion to produce the same amount of energy.
B) Fusion reactions decrease the overall number of particles in the core, causing the core to shrink, converting gravitational potential energy into thermal energy, and increasing the rate of fusion.
C) The radiation produced by fusion reactions that is trapped in the core gradually raises the temperature, increasing the rate of fusion.
D) The Sun gets heavier as it gets older, and the stronger inward pull of gravity increases the fusion rate.
E) The rate of fusion is not rising; it is actually decreasing over time.

B

26) Suppose that, for some unknown reason, the core of the Sun suddenly became hotter. Which of the following best describes what would happen?
A) Higher temperature would cause the rate of nuclear fusion to rise, which would increase the internal pressure, causing the core to expand and turn the Sun into a giant star.
B) Higher temperature would cause the rate of nuclear fusion to rise, which would increase the internal pressure, causing the core to expand and cool until the fusion rate returned to normal.
C) Higher temperature would cause the rate of fusion to fall, decreasing the internal pressure and causing the core to collapse until the rate of fusion returned to normal.
D) The higher temperature would not affect the fusion rate but would cause the core to expand and cool until the temperature returned to normal, with the core at a new, slightly larger size.

B

27) How do we know what goes on under the surface of the Sun?
A) We have X-ray images from satellites of the interior of the Sun.
B) Astronomers create mathematical models that use the laws of physics, the Sun's observed composition and mass, and computers to predict internal conditions.
C) We have sent probes below the surface of the Sun.
D) By measuring Doppler shifts, we observe vibrations of the Sun's surface that are created deep within the Sun.
E) both B and D

E

28) Studies of sunquakes, or helioseismology, have revealed that
A) the Sun vibrates only on the surface.
B) "sunquakes" are caused by similar processes that create earthquakes on Earth.
C) the Sun generates energy by nuclear fusion.
D) our mathematical models of the solar interior are fairly accurate.
E) neutrinos from the solar core reach the solar surface easily.

D

29) Which statement best describes the solar neutrino problem?
A) Theoretical models predict that neutrinos should be produced in the Sun, but no neutrinos have ever been observed to be coming from the Sun.
B) Solar neutrinos have been detected, but in fewer numbers than predicted by theoretical models.
C) No one understands how it can be possible for neutrinos to be produced in the Sun.
D) Our current understanding of fusion in the Sun suggests that all neutrinos should be destroyed before they arrive at Earth, yet neutrinos are being detected.
E) The term solar neutrino problem refers to the fact that neutrinos are extremely difficult to detect.

B

30) Why are neutrinos so difficult to detect?
A) because there are so rare
B) because they have no mass
C) because they move at nearly the speed of light
D) because they rarely interact with matter
E) because they are so small

D

31) Which of the following statements about neutrinos is not true?
A) About a thousand trillion neutrinos are passing through your body every second.
B) Neutrinos are created as a by-product of the proton-proton chain.
C) Neutrinos have no electrical charge.
D) Neutrinos have a tendency to pass through just about anything without interactions, making them very difficult to detect.
E) The mass of a neutrino is 30 percent of the mass of an electron.

E

32) What is a possible solution to the solar neutrino problem?
A) The Sun is generating energy other than by nuclear fusion.
B) The Sun is generating much less energy than we think it is.
C) We do not know how to detect electron neutrinos.
D) Not all fusion reactions create electron neutrinos.
E) The electron neutrinos created in the Sun change into another type of neutrino that we do not detect.

E

33) The light radiated from the Sun's surface reaches Earth in about 8 minutes, but the energy of that light was released by fusion in the solar core about
A) one year ago.
B) ten years ago.
C) a hundred years ago.
D) a thousand years ago.
E) a million years ago.

E

34) What happens to energy in the convection zone of the Sun?
A) Energy slowly leaks outward through the diffusion of photons that repeatedly bounce off ions and electrons.
B) Energy is produced in the convection zone by nuclear fusion.
C) Energy is transported outward by the rising of hot plasma and the sinking of cooler plasma.
D) Energy is consumed in the convection zone by the creation of electrons and positrons.
E) Energy is conserved so while the gas moves up and down, there is no net transport of energy.

C

35) Most of the energy produced in the Sun is released in the form of visible light from the photosphere. However, some energy is released from the upper layers of the solar atmosphere. Which of the following best describes where other forms of light are released?
A) The chromosphere is the source of ultraviolet light, and the corona is the source of X rays.
B) The chromosphere is the source of infrared light, and the corona is the source of ultraviolet light.
C) The chromosphere is the source of X rays, and the corona is the source of radio waves.
D) The convection zone is the source of ultraviolet light, and the upper photosphere is the source of X rays.
E) Radio waves can pass directly through the gas which allows us to see the core.

A

36) What is granulation in the Sun?
A) the bubbling pattern on the photosphere produced by the underlying convection
B) another name for the way sunspots look on the surface of the Sun
C) elements in the Sun other than hydrogen and helium
D) dust particles in the Sun that haven't been turned into plasma
E) lumps of denser material in the Sun

A

37) What are coronal holes?
A) regions on the photosphere where magnetic lines poke through, creating the cooler areas of the sunspots
B) areas of the corona where magnetic field lines project into space, allowing charged particles to escape the Sun, becoming part of the solar wind
C) holes in the corona of the Sun that allow us to see the photosphere
D) tunnels in the outer layers of the Sun through which photons can escape more quickly than through the radiation zone
E) all of the above

B

38) Which of the following statements about the sunspot cycle is not true?
A) The number of sunspots peaks approximately every 11 years.
B) With each subsequent peak in the number of sunspots, the magnetic polarity of the Sun is the reverse of the previous peak.
C) The rate of nuclear fusion in the Sun peaks about every 11 years.
D) The cycle is truly a cycle of magnetic activity, and variations in the number of sunspots are only one manifestation of the cycle.
E) The number of solar flares peaks about every 11 years.

C

39) What processes are involved in the sunspot cycle?
A) gravitational contraction of the Sun
B) wave motions in the solar interior
C) variations of the solar thermostat
D) the winding of magnetic field lines due to differential rotation
E) the interaction of the Earth's magnetic field with that of the Sun

D

40) What observations characterize solar maximum?
A) The Sun becomes much brighter.
B) The Sun emits light of longer average wavelength.
C) The Sun rotates faster at the equator.
D) We see many sunspots on the surface of the Sun.
E) all of the above

D

41) Humans have not sent a spacecraft into the interior of the Sun to confirm any models of the interior. What evidence then do we have to support our current ideas about the solar interior?
A) solar neutrinos
B) solar flares
C) sun spots
D) X-ray observations that penetrate the gas
E) We have no evidence, just informed guesses.

A

) Gravitational equilibrium means that the surface and the core of the Sun are at the same pressure.

Answer: FALSE

Although the Sun does not generate energy by gravitational contraction today, this energy-generation mechanism was important when the Sun was forming.

Answer: TRUE

The Sun generates energy primarily by nuclear fission.

Answer: FALSE

Nuclear power plants on Earth create energy in the same way as the Sun.

Answer: FALSE

The corona and chromosphere are hotter than the photosphere.

Answer: TRUE

The chromosphere is the layer of the Sun that we see as its visible surface.

Answer: FALSE

Energy from the core of the Sun first travels slowly through the convection zone and then much faster through the radiation zone.

Answer: FALSE

Sunspots are cooler than the surrounding region of the Sun's surface.

Answer: TRUE

The core of the Sun is at a temperature of about 20,000 K.

Answer: FALSE

) The Sun's rate of fusion is gradually increasing over time.

Answer: TRUE

The Sun is a relatively young star, near the beginning of its life.

Answer: FALSE

1) According to modern science, approximately how old is the Sun?
A) 4.5 billion years
B) 25 million years
C) 10,000 years
D) 400 million years

A

2) The Sun will exhaust its nuclear fuel in about
A) 5000 AD.
B) 5 million years.
C) 5 billion years.
D) 50 billion years.

C

3) Which of the following correctly describes how the process of gravitational contraction can make a star hot?
A) Gravitational contraction involves nuclear fusion, which generates a lot of heat.
B) When a star contracts in size, gravitational potential energy is converted to thermal energy.
C) Heat is generated when gravity contracts, because gravity is an inverse square law force.
D) Gravitational contraction involves the generation of heat by chemical reactions, much like the burning of coal.

B

5) The source of energy that keeps the Sun shining today is
A) nuclear fission.
B) gravitational contraction.
C) chemical reactions.
D) nuclear fusion.

D

6) When we say that the Sun is a ball of plasma, we mean that
A) the Sun is made of material that acts like a liquid acts on Earth.
B) the Sun is made of atoms and molecules.
C) the Sun consists of gas in which many or most of the atoms are ionized (missing electrons).
D) the Sun is roughly the same color as blood.

C

7) What is the Sun made of (by mass)?
A) 70% hydrogen, 28% helium, 2% other elements
B) 100% hydrogen and helium
C) 50% hydrogen, 25% helium, 25% other elements
D) 90% dark matter, 10% ordinary matter

A

8) From center outward, which of the following lists the "layers" of the Sun in the correct order?
A) core, radiation zone, convection zone, corona, chromosphere, photosphere
B) core, convection zone, radiation zone, corona, chromosphere, photosphere
C) core, radiation zone, convection zone, photosphere, chromosphere, corona
D) core, corona, radiation zone, convection zone, photosphere, chromosphere

C

10) The Sun's surface, as we see it with our eyes, is called the
A) chromosphere.
B) photosphere.
C) corona.
D) core.

B

11) The Sun's average surface (photosphere) temperature is about
A) 1,000,000 K.
B) 5,800 K.
C) 1,000 K.
D) 37,000 K.

B

What is the solar wind?
A) the uppermost layer of the Sun, lying just above the corona
B) the strong wind that blows sunspots around on the surface of the Sun
C) the wind that causes huge arcs of gas to rise above the Sun's surface
D) a stream of charged particles flowing outward from the surface of the Sun

D

13) The fundamental nuclear reaction occurring in the core of the Sun is
A) nuclear fission.
B) radioactive decay.
C) nuclear fusion of hydrogen into helium.
D) nuclear fusion of helium to carbon.

C

14) The proton-proton chain is
A) the specific set of nuclear reactions through which the Sun fuses hydrogen into helium.
B) the linkage of numerous protons into long chains.
C) another name for the force that holds protons together in atomic nuclei.
D) an alternative way of generating energy that is different from the fusion of hydrogen into helium.

A

16) To estimate the central temperature of the Sun, scientists
A) send probes to measure the temperature.
B) use hot gas to create a small Sun in a laboratory.
C) monitor changes in Earth's atmosphere.
D) use computer models to predict interior conditions.

D

18) Which statement best describes what was called the solar neutrino problem?
A) Early experiments designed to detect solar neutrinos found them, but in fewer numbers than had been expected.
B) It referred to the fact that neutrinos are extremely difficult to detect.
C) Our understanding of fusion in the Sun suggested that neutrinos should be destroyed before they arrive at Earth, yet neutrinos were being detected.
D) No one understood how it could be possible for neutrinos to be

A

19) The light radiated from the Sun's surface reaches Earth in about 8 minutes, but the energy of that light was released by fusion in the solar core about
A) three days ago.
B) one hundred years ago.
C) one thousand years ago.
D) a few hundred thousand years ago.

D

20) What happens to energy in the Sun's convection zone?
A) Energy is produced in the convection zone by thermal radiation.
B) Energy is transported outward by the rising of hot plasma and sinking of cooler plasma.
C) Energy slowly leaks outward through the radiative diffusion of photons that repeatedly bounce off ions and electrons.
D) Energy is produced in the convection zone by nuclear fusion.

B

21) What do sunspots, solar prominences, and solar flares all have in common?
A) They all have about the same temperature.
B) They are all shaped by the solar wind.
C) They are all strongly influenced by magnetic fields on the Sun.
D) They all occur only in the Sun's photosphere.

C

22) Which of the following is not a characteristic of the 11-year sunspot cycle?
A) The sunspot cycle is very steady, so that each 11-year cycle is nearly identical to every other 11-year cycle.
B) The likelihood of seeing solar prominences or solar flares is higher when sunspots are more common and lower when they are less common.
C) The Sun's entire magnetic field flip-flops at the end of each cycle (at solar minimum).
D) The number of sunspots on the Sun at any one time gradually rises and falls, with an average of 11 years between the times when sunspots are most numerous.

A

23) How is the sunspot cycle directly relevant to us here on Earth?
A) The sunspot cycle strongly influences Earth's weather.
B) The Sun's magnetic field, which plays a major role in the sunspot cycle, affects compass needles that we use on Earth.
C) The brightening and darkening of the Sun that occurs during the sunspot cycle affects plant photosynthesis here on Earth.
D) Coronal mass ejections and other activity associated with the sunspot cycle can disrupt radio communications and knock out sensitive electronic equipment.
E) The sunspot cycle is the cause of global warming.

D

2) When is/was gravitational contraction an important energy generation mechanism for the Sun?
A) It was important when the Sun was forming from a shrinking interstellar cloud of gas.
B) It is the primary energy generation mechanism in the Sun today.
C) It has played a role throughout the Sun's history, but it was most important right after nuclear fusion began in the Sun's core.
D) It is important during periods when the Sun is going from solar maximum to solar minimum.

A

3) What do we mean when we say that the Sun is in gravitational equilibrium?
A) The Sun maintains a steady temperature.
B) There is a balance within the Sun between the outward push of pressure and the inward pull of gravity.
C) The hydrogen gas in the Sun is balanced so that it never rises upward or falls downward.
D) The Sun always has the same amount of mass, creating the same gravitational force.

B

5) How does the Sun's mass compare to Earth's mass?
A) The Sun's mass is about 300 times the mass of Earth.
B) The Sun's mass is about 30 times the mass of Earth.
C) The Sun's mass is about 300,000 times the mass of Earth.
D) Both have approximately the same mass.

C

6) Which of the following best describes why the Sun emits most of its energy in the form of visible light?
A) Nuclear fusion in the Sun's core produces visible light photons.
B) The visible light comes from energy level transitions as electrons in the Sun's hydrogen atoms jump between level 1 and level 2.
C) Like all objects, the Sun emits thermal radiation with a spectrum that depends on its temperature, and the Sun's surface temperature is just right for emitting mostly visible light.
D) The Sun's gas is on fire like flames from wood or coal, and these flames emit visible light.

C

7) The Sun's surface seethes and churns with a bubbling pattern. Why?
A) The Sun's surface is boiling.
B) The churning gas is being stirred up by the strong solar wind.
C) The churning is an illusion created by varying radiation, as the gas on the Sun's surface is actually quite still.
D) We are seeing hot gas rising and cool gas falling due to the convection that occurs beneath the surface.

D

8) Which of the following correctly compares the Sun's energy generation process to the energy generation process in human-built nuclear power plants?
A) The Sun generates energy by fusing small nuclei into larger ones, while our power plants generate energy by the fission (splitting) of large nuclei.
B) Both processes involve nuclear fusion, but the Sun fuses hydrogen while nuclear power plants fuse uranium.
C) The Sun generates energy through nuclear reactions while nuclear power plants generate energy through chemical reactions.
D) The Sun generates energy through fission while nuclear power plants generate energy through fusion.

A

9) Every second, the Sun converts about 600 million tons of hydrogen into 596 million tons of helium. The remaining 4 million tons of mass is
A) ejected into space in a solar wind.
B) ejected into space by solar flares.
C) converted to an amount of energy equal to 4 million tons times the speed of light squared.
D) reabsorbed as molecular hydrogen.

C

10) Which of the following best explains why nuclear fusion requires bringing nuclei extremely close together?
A) Nuclei normally repel because they are all positively charged and can be made to stick only when brought close enough for the strong force to take hold.
B) Nuclei are attracted to each other by the electromagnetic force, but this force is only strong enough to make nuclei stick when they are very close together.
C) Nuclei have to be very hot in order to fuse, and the only way to get them hot is to bring them close together.
D) Fusion can proceed only by the proton-proton chain, and therefore requires that protons come close enough together to be linked up into a chain.

A

If the Sun's core suddenly shrank a little bit, what would happen in the Sun?
A) The core would cool off and continue to shrink as its density increased.
B) The density of the core would decrease, causing the core to cool off and expand.
C) The core would heat up, causing it to radiate so much energy that it would shrink even more.
D) The core would heat up, fusion rates would increase, and the core would re-expand.

D

12) Why does the Sun emit neutrinos?
A) Solar flares create neutrinos with magnetic fields.
B) Fusion in the Sun's core creates neutrinos.
C) Convection releases neutrinos, which random walk through the radiation zone.
D) The Sun was born with a supply of neutrinos that it gradually emits into space.
E) The Sun does not emit neutrinos.

B

13) If the Sun suddenly stopped emitting neutrinos, what might we infer (after checking that our neutrino detectors were still operational)?
A) Fusion reactions in the Sun ceased a few hundred thousand years ago.
B) Fission reactions in the Sun have ceased.
C) Fusion reactions in the Sun have ceased.
D) The Sun has exhausted its supply of neutrinos.

C

14) Which of the following best explains why the Sun's luminosity gradually rises over billions of years?
A) Fusion gradually decreases the number of independent particles in the core, allowing gravity to compress and heat the core, which in turn increases the fusion rate and the Sun's luminosity.
B) Nuclear reactions in the Sun become more efficient with time, so that each fusion reaction releases more energy when the Sun is old than when it is young; this in turn raises the Sun's luminosity.
C) The Sun's core gradually expands with time, and this expansion means there is more room for energy to be generated and hence increases the Sun's luminosity.
D) The planets need more and more energy to maintain any life on them as time goes on, and therefore the Sun must bet hotter.

A

15) Why do sunspots appear dark in pictures of the Sun?
A) They are too cold to emit any visible light.
B) They are holes in the solar surface through which we can see through to deeper, darker layers of the Sun.
C) They are extremely hot and emit all their radiation as X rays rather than visible light.
D) They actually are fairly bright, but appear dark against the even brighter background of the surrounding photosphere.

D

6) Which of the following best describes the current status of our understanding of the solar neutrino problem?
A) Experimental evidence indicates that the problem is solved and the expected number of solar neutrinos are indeed being produced by the Sun.
B) The problem arose only because experimental data were being misinterpreted; on re-examination, the old data showed that the expected number of neutrinos were being detected.
C) We have learned that the Sun's interior undergoes fusion at a lower rate than we had expected, and that is why we had observed fewer neutrinos than expected.
D) The solar neutrino problem remains as perplexing as ever, and indeed makes everything we think we know about stars suspect.

A

17) How can we best observe the Sun's chromosphere and corona?
A) The chromosphere is best observed with infrared telescopes and the corona is best observed with ultraviolet telescopes.
B) The chromosphere is best observed with ultraviolet telescopes and the corona is best observed with X-ray telescopes.
C) The chromosphere and corona are both best studied with visible light.
D) The chromosphere and corona are both best studied with radio telescopes.

B

18) The intricate patterns visible in an X-ray image of the Sun generally show
A) helioseismological fluctuations.
B) a bubbling pattern on the photosphere.
C) extremely hot plasma flowing along magnetic field lines.
D) structure within sunspots.

C

19) How can we measure the strength of magnetic fields on the Sun?
A) by looking for the splitting of spectral lines in the Sun's spectrum
B) by observing the sizes of sunspots: Bigger sunspots mean a stronger field
C) by observing auroras here on Earth
D) only by using sophisticated computer models, because there are no observational ways of measuring magnetic field strength

A

satellites in low-Earth orbits are more likely to crash to Earth when the sunspot cycle is near solar maximum because
A) it is too dangerous to send the Space Shuttle to service satellites during solar maximum.
B) Earth's upper atmosphere tends to expand during solar maximum, exerting drag on satellites in low orbits.
C) of increased magnetic interference.
D) they are more likely to have their electronics "fried" by a solar flare during solar maximum.

B

21) Which of the following choices is not a way by which we can study the inside of the Sun?
A) We can probe the interior of the Sun by studying the vibrations in its photosphere.
B) We can make a computer model of the Sun's interior that allow us to predict the observable properties of the Sun.
C) We can send a space probe into the Sun's photosphere.
D) We can study solar neutrinos.

C

22) A computer accessory salesman attempts to convince you to purchase a "solar neutrino" shield for your new computer. (It's even "on sale"!) Why do you turn down this excellent offer?
A) There's no such thing as a solar neutrino.
B) Solar neutrinos are generated by solar winds, but we're in a solar minimum now, so the risk of damage is very low.
C) The Earth's natural magnetic field already offers excellent protection against the onslaught of solar neutrinos.
D) Neutrinos rarely, if ever, interact with your computer.

D