Question 1

Which of the following statements best describes the significance of Maxwell’s addition to Ampère’s law?

Accepted Answer

It established that a changing electric field produces a magnetic field, allowing electromagnetic waves to propagate.

Question 2

A radio station transmits at a frequency of $$100\ \mathrm{MHz}. $$What is the wavelength of the electromagnetic wave it emits? (Take the speed of light $$c = 3.00 	imes 10^8$\ \mathrm{m/s})$$

Accepted Answer

$$3.00\ \mathrm{m}$$

Question 3

Which of the following best describes the orientation of the electric and magnetic fields in an electromagnetic wave propagating through free space?

Accepted Answer

The electric and magnetic fields are perpendicular to each other and to the direction of propagation.

Question 4

Which equation correctly relates the speed of light $$c to $$the permittivity $$\$$varepsilon_0$$ and permeability $$\$$mu_0 of $$free space?

Accepted Answer

$$c = 1 / \sqrt{\$$varepsilon_0$$ \mu_0$}$$

Question 5

A laser beam has an average intensity of $$I = 500\ \mathrm{W/m^2$}$$ and is fully absorbed by a surface. What is the radiation pressure exerted on the surface?

Accepted Answer

$$p = \dfrac{I}{c}$$

Question 6

Which of the following is NOT a consequence of electromagnetic waves carrying momentum?

Accepted Answer

Electromagnetic waves can create magnetic monopoles.

Question 7

Which part of the electromagnetic spectrum has the shortest wavelength?

Accepted Answer

Gamma rays

Question 8

A sinusoidal electromagnetic wave in free space has a peak electric field $$E_0 = 100$$\ \mathrm{V/m}$$. What is the corresponding peak magnetic field B_0$?

Accepted Answer

$$B_0$$ = \dfrac{$$E_0$$}{c}$$

Question 9

Which of the following best describes how information is transmitted in amplitude modulation (AM) radio?

Accepted Answer

The amplitude of the carrier wave is varied in accordance with the audio signal.

Question 10

A microwave oven operates at a frequency of $$2.45\ \mathrm{GHz}. $$What is the wavelength of the microwaves used? (Use $$c = 3.00 	imes 10^8$\ \mathrm{m/s})$$

Accepted Answer

$$0.122\ \mathrm{m}$$

Question 11

Which of the following experiments provided early evidence that the speed of light is finite?

Accepted Answer

Observations of Jupiter’s moons’ orbits

Question 12

The energy density $$u of an $$electromagnetic wave is given by:

Accepted Answer

$$u = \dfrac{1}{2} \$$varepsilon_0$$ E^2$ + \dfrac{1}{2} \dfrac{B^2$}{\mu_0$}$$

Question 13

If the average intensity of sunlight at Earth’s surface is $$I = 1000\ \mathrm{W/m^2$}$$, what is the average energy delivered to a $$2\ \mathrm{m^2$}$$ solar panel in $$10\ \mathrm{s}$$?

Accepted Answer

$$20,000\ \mathrm{J}$$

Question 14

Which of the following is true about the relationship between wavelength $$\lambda$$ and frequency $$f$$ for electromagnetic waves?

Accepted Answer

$$f = \dfrac{c}{\lambda}$$

Question 15

A $$10\ \mathrm{W}$$ radio transmitter emits uniformly in all directions. What is the intensity at a distance of $$100\ \mathrm{m}$$ from the transmitter?

Accepted Answer

$$I = \dfrac{10}{4 \pi (100)^2$}\ \mathrm{W/m^2$}$$

Question 16

Which of the following best explains why electromagnetic waves can travel through the vacuum of space?

Accepted Answer

They are self-propagating due to the interplay of changing electric and magnetic fields.

Question 17

If an electromagnetic wave is fully reflected by a surface, how does the radiation pressure compare to the case where it is fully absorbed?

Accepted Answer

It is twice as much.

Question 18

Which of the following is a correct statement about the electromagnetic spectrum?

Accepted Answer

Radio waves have lower frequencies than ultraviolet light.

Question 19

A television signal is transmitted using frequency modulation (FM). Which of the following best describes this process?

Accepted Answer

The frequency of the carrier wave is varied by the signal.

Question 20

Which of the following best describes the role of a tuner in a radio receiver?

Accepted Answer

It selects the desired frequency from among many present.

Chpt 22

Study Guide - Practice Questions

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