Our bodies are penetrated by x-rays but not by visible light. Is this because x-rays travel faster than visible light?

No

List the following types of electromagnetic radiation in order of decreasing wavelength:

(a) The gamma rays produced by a radioactive nuclide used in medical imaging
(b) Radiation from an FM radio station at 93.1 MHzon the dial
(c) A radio signal from an AM radio station at 680 kHz on the dial
(d) The yellow light from sodium vapor streetlights
(e) The red light of a light-emitting diode, such as in a calculator display

Highest --> Lowest

(c) A radio signal from an AM radio station at 680 kHz on the dial

(b) Radiation from an FM radio station at 93.1 MHzon the dial

(e) The red light of a light-emitting diode, such as in a calculator display

(d) The yellow light from sodium vapor streetlights

(a) The gamma rays produced by a radioactive nuclide used in medical imaging

Assuming equal efficiency of conversion, would infrared or ultraviolet radiation yield more electrical energy on a per-photon basis?

Ultraviolet radiation

The frequency of radiation increases as the wavelength increases.

True or false

False

The frequency of radiation decreases as the wavelength increases.

Electromagnetic radiation travels through a vacuum at a constant speed, regardless of wavelength.

True of false

True

Infrared light has higher frequencies than visible light.

True or false

False

Infrared light has lower frequencies than visible light.

The glow from a fireplace, the energy within a microwave oven, and a foghorn blast are all forms of electromagnetic radiation.

True or false

False

A foghorn blast is a form of sound waves, which are not accompanied by oscillating electric and magnetic fields.

Suppose that the microwave radiation has a wavelength of 11.6 cm . How many photons are required to heat 275 mL of coffee from 25.0 ∘C to 62.0 ∘C? Assume that the coffee has the same density, 0.997 g/mL , and specific heat capacity, 4.184 J/(g⋅K), as water over this temperature range.

2.48×10²⁸ photons

Electromagnetic radiation in this region of the spectrum is also used for cellular phones, radar, and wireless Internet.

If human height were quantized in one-foot increments, what would happen to the height of a child as she grows up?

Quantization means that changes can only happen in certain allowed increments. If the human growth quantum is one-foot, growth occurs instantaneously in one-foot increments. That is, a child experiences growth spurts of one-foot; her height changes by one-foot increments.

Sodium metal requires a photon with a minimum energy of 4.41×10−19J to emit electrons.

What is the minimum frequency of light necessary to emit electrons from sodium via the photoelectric effect?

u = 6.66×10¹⁴ s−1

What is the wavelength of this light?

u = 6.66×10¹⁴ s−1

λ = 450 nm

If sodium is irradiated with light of 405 nm, what is the maximum possible kinetic energy of the emitted electrons?

E = 4.90×10⁻²⁰ J

What is the maximum number of electrons that can be freed by a burst of light of 405 nm whose total energy is 1.00 μJ?

HINT: One electron can be ejected per photon

N = 2.04×10¹² electrons

One type of sunburn occurs on exposure to UV light of wavelength in the vicinity of 325 nm .

What is the energy of a photon of this wavelength?

E = 6.11×10⁻¹⁹ J

What is the energy of a mole of these photons?

E = 6.11×10⁻¹⁹ J

E = 3.68×10⁵ J

How many photons are in a 1.10 mJ burst of this radiation?

N = 1.80×10¹⁵ photons

These UV photons can break chemical bonds in your skin to cause sunburn—a form of radiation damage. If the 325 nm radiation provides exactly the energy to break an average chemical bond in the skin, estimate the average energy of these bonds in kJ/mol.

Average bond energy = 368 kJ/mol