Q: The speed of electromagnetic waves in a vacuum is given by $$c = \frac{1}{\sqrt{\mu_0$ \$$epsilon_0$$}}. $$What are the values of $$\mu_0$ and $$\$$epsilon_0$$?

$$\mu_0$ = 4\pi \times 10$$^{-7}$$ \ \mathrm{N\cdot s^2$/C^2$$}$$ and $$\$$epsilon_0 = 8.85$$ \times $$10^{-12}$$ \ \mathrm{$$C^2/N$$\cdot $$m^2$$}$

Q: A beam of sunlight has an intensity of $$1350\ \mathrm{W/m^2$} at $$the top of Earth’s atmosphere. What is the maximum value of the electric field $$E_0 in $$this wave?

$$E_0 = 1.01$$ \times $$10^3$$\ \mathrm{V/m}$$

Q: A 1.0 m$$^2$$ solar sail is placed at Earth’s distance from the Sun and is perfectly reflective. What is the approximate force exerted on the sail by sunlight? (Assume $$I = 1350\ \mathrm{W/m^2$}$$ and $$c = 3.0 \times 10^8$\ \mathrm{m/s}.)$$

$$9.0 \times 10$$^{-6}$$\ \mathrm{N}$$

Question 1

Which of the following best describes the difference between radio waves and X-rays?

Accepted Answer

Both can be thought of as electromagnetic waves. They differ only in wavelength and frequency.

Question 2

Maxwell’s equations unified the phenomena of electricity and magnetism. Which of the following is NOT a consequence of Maxwell’s equations?

Accepted Answer

Electric field lines are always continuous and do not begin or end.

Question 3

According to Maxwell’s theory, what is required for the production of electromagnetic waves?

Accepted Answer

An accelerating electric charge.

Question 4

The speed of electromagnetic waves in a vacuum is given by $$c = \frac{1}{\sqrt{\mu_0$ \$$epsilon_0$$}}. $$What are the values of $$\mu_0$ and $$\$$epsilon_0$$?

Accepted Answer

$$\mu_0$ = 4\pi 	imes 10$$^{-7}$$ \ \mathrm{N\cdot s^2$/C^2$$}$$ and $$\$$epsilon_0 = 8.85$$ 	imes $$10^{-12}$$ \ \mathrm{$$C^2/N$$\cdot $$m^2$$}$

Question 5

A 93.3 MHz FM radio wave travels through space. What is its wavelength?

Accepted Answer

$$3.22\ \mathrm{m}$$

Question 6

Which of the following statements about electromagnetic waves is correct?

Accepted Answer

They are transverse waves that can propagate in a vacuum.

Question 7

The energy density $$u of an $$electromagnetic wave is given by $$u = \$$epsilon_0$$ E^2$. What is the average intensity I$ of the wave in terms of the maximum electric field E_0$?

Accepted Answer

$$I = \frac{1}{2} \$$epsilon_0$$ c E_0$^2$$

Question 8

A beam of sunlight has an intensity of $$1350\ \mathrm{W/m^2$} at $$the top of Earth’s atmosphere. What is the maximum value of the electric field $$E_0 in $$this wave?

Accepted Answer

$$E_0 = 1.01$$ 	imes $$10^3$$\ \mathrm{V/m}$$

Question 9

If the intensity of an electromagnetic wave doubles, what happens to the amplitude of the electric field?

Accepted Answer

It increases by a factor of $$\sqrt{2}.$$

Question 10

A satellite dish focuses electromagnetic waves onto a receiver. Which property of the dish is most important for maximizing the received signal?

Accepted Answer

The dish’s diameter relative to the wavelength of the signal.

Question 11

A 1.0 m$$^2$$ solar sail is placed at Earth’s distance from the Sun and is perfectly reflective. What is the approximate force exerted on the sail by sunlight? (Assume $$I = 1350\ \mathrm{W/m^2$}$$ and $$c = 3.0 	imes 10^8$\ \mathrm{m/s}.)$$

Accepted Answer

$$9.0 	imes 10$$^{-6}$$\ \mathrm{N}$$

Question 12

Which of the following best explains why AM radio signals can be detected more readily than FM signals behind hills or buildings?

Accepted Answer

AM signals have longer wavelengths and thus diffract more.

Question 13

A radio station broadcasts at 100.1 MHz. What is the wavelength of the carrier wave?

Accepted Answer

$$2.99\ \mathrm{m}$$

Question 14

Which of the following is NOT a property of electromagnetic waves?

Accepted Answer

Their electric and magnetic fields are parallel to the direction of propagation.

Question 15

A coaxial cable is used to transmit electromagnetic signals. Compared to the speed of light in vacuum, the speed of signals in the cable is:

Accepted Answer

Slightly less, due to the permittivity and permeability of the cable’s material.

Question 16

Which of the following best describes the process of amplitude modulation (AM) in radio transmission?

Accepted Answer

The amplitude of the carrier wave is varied in proportion to the audio signal.

Question 17

A television broadcast from the Moon was received live on Earth. Which property of electromagnetic waves made this possible?

Accepted Answer

EM waves can travel through the vacuum of space.

Question 18

If a radio wave and an X-ray are both traveling in a vacuum, which of the following is always the same for both?

Accepted Answer

Speed

Question 19

A 1.0 kHz electromagnetic wave and a 1.0 kHz sound wave are both produced. Which statement is correct?

Accepted Answer

The EM wave travels much faster than the sound wave.

Electromagnetic Waves: Maxwell’s Theory, Production, Properties, and Applications

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