Deck 24: Electromagnetic Waves

Question 1

Complete the following sentence: When electrons from a heated filament accelerate through vacuum toward a positive plate,

A)only an electric field will be produced.
B)only a magnetic field will be produced.
C)electromagnetic waves will be produced.
D)longitudinal waves will be produced.
E)neither electric nor magnetic fields will be produced.

Answer 1

electromagnetic waves will be produced.

Question 2

When a radio telescope observes a region of space between two stars, it detects electromagnetic radiation that has a wavelength of 0.21 m. This radiation was emitted by hydrogen atoms in the gas and dust located in that region. What is the frequency of this radiation?

A)7.1 × 10¹⁰ Hz
B)2.1 × 10¹⁴ Hz
C)3.0 × 10⁸ Hz
D)6.9 × 10¹¹ Hz
E)1.4 × 10⁹ Hz

Answer 2

1.4 × 10⁹ Hz

Question 3

Which one of the following colors of visible light has the highest frequency?

A)yellow
B)red
C)green
D)blue
E)violet

Answer 3

violet

Question 4

Which one of the following will not generate electromagnetic waves or pulses?

A)a steady direct current
B)an accelerating electron
C)a proton in simple harmonic motion
D)an alternating current
E)charged particles traveling in a circular path in a mass spectrometer

Question 5

The average distance between the surface of the earth and the surface of the sun is 1.49 × 10¹¹ m. How much time, in minutes, does it take light leaving the surface of the sun to reach the earth?

A)zero minutes
B)2.9 × 10^-3 min
C)8.3 min
D)74 min
E)500 min

Question 6

A distant space probe is programmed to emit a radio signal toward Earth at regular time intervals. One such pulse arrives on Earth 6.92 s after it is emitted from the probe. What is the approximate distance from the Earth to the probe?

A)8.76 × 10⁹ m
B)7.40 × 10¹⁰ m
C)6.94 × 10⁹ m
D)2.08 × 10⁹ m
E)3.50 × 10¹⁰ m

Question 7

Which one of the following wavelengths is in the infrared range of the electromagnetic spectrum?

A)100 mm
B)400 nm
C)400 m
D)2 × 10^-15 m
E)20 µm

Question 8

An FM radio station generates radio waves that have a frequency of 101.3 MHz. The frequency of the waves from a competing station have a frequency of 107.1 MHz. What is the difference in wavelength between the waves emitted from the two stations?

A)0.22 m
B)0.45 m
C)0.84 m
D)2.4 m
E)0.16 m

Question 9

Which one of the following statements concerning electromagnetic waves is false?

A)Electromagnetic waves carry energy.
B)X-rays have longer wavelengths than radio waves.
C)In vacuum, all electromagnetic waves travel at the same speed.
D)Lower frequency electromagnetic waves can be produced by oscillating circuits.
E)They consist of mutually perpendicular electric and magnetic fields that oscillate perpendicular to the direction of propagation.

Question 10

Which one of the following scientists did not attempt to measure the speed of light?

A)Galileo
B)Maxwell
C)Fizeau
D)Foucault
E)Michelson

Question 11

Note the different types of electromagnetic radiation: Which list correctly ranks the electromagnetic waves in order of increasing frequency?

A)2, 3, 4, 5, 6, 1
B)2, 5, 4, 1, 6, 3
C)2, 5, 4, 6, 1, 3
D)3, 1, 6, 4, 5, 2
E)3, 6, 1, 4, 5, 2

Question 12

Complete the following sentence: The various colors of visible light differ in

A)frequency only.
B)wavelength only.
C)their speeds in a vacuum.
D)both frequency and wavelength.
E)both frequency and their speed in a vacuum.

Question 13

Which one of the following types of wave is fundamentally different than the other four?

A)radio waves
B)sound waves
C)gamma rays
D)ultraviolet radiation
E)visible light

Question 14

The electric field E of an electromagnetic wave traveling the positive x direction is illustrated in the figure. This is the wave of the radiation field of an antenna. What are the direction and the phase relative to the electric field of the magnetic field at a point where the electric field is in the negative y direction? Note: The wave is shown in a region of space that is a large distance from its source.

A)+y direction, in phase
B)-z direction, 90° out of phase
C)+z direction, 90° out of phase
D)-z direction, in phase
E)+z direction, in phase

Question 15

A radio wave sent from the surface of the earth reflects from the surface of the moon and returns to the earth. The elapsed time between the generation of the wave and the detection of the reflected wave is 2.6444 s. Determine the distance from the surface of the earth to the surface of the moon. Note: The speed of light is 2.9979 × 10⁸ m/s.

A)3.7688 × 10⁸ m
B)3.8445 × 10⁸ m
C)3.9638 × 10⁸ m
D)4.0551 × 10⁸ m
E)7.9276 × 10⁸ m

Question 16

Which one of the following statements concerning the wavelength of an electromagnetic wave in a vacuum is true?

A)The wavelength is independent of the speed of the wave for a fixed frequency.
B)The wavelength is inversely proportional to the speed of the wave.
C)The wavelength is the same for all types of electromagnetic waves.
D)The wavelength is directly proportional to the frequency of the wave.
E)The wavelength is inversely proportional to the frequency of the wave.

Question 17

Which one of the following statements concerning electromagnetic waves is false?

A)Electromagnetic waves are longitudinal waves.
B)Electromagnetic waves transfer energy through space.
C)The existence of electromagnetic waves was predicted by Maxwell.
D)Electromagnetic waves can propagate through a material substance.
E)Electromagnetic waves do not require a physical medium for propagation.

Question 18

What is the correct order, beginning with shortest wavelength and extending to the longest wavelength, of the following colors in the visible light spectrum: blue, green, red, violet, and yellow?

A)red, yellow, blue, green, violet
B)violet, blue, yellow, red, green
C)red, yellow, green, blue, violet
D)violet, blue, green, yellow, red
E)red, blue, violet, green, yellow

Question 19

In 1980, a television station began broadcasting on channel 32 at a frequency of 582 MHz. The circuit contains an inductor with an inductance L = 4.15 × 10^-4 H and a variable-capacitance C. Determine the value of C that allows this television station to be tuned in.

A)2.92 × 10^-12 F
B)5.84 × 10^-12 F
C)1.80 × 10^-12 F
D)3.61 × 10^-11 F
E)1.10 × 10^-11 F

Question 20

A cellular telephone transmits electromagnetic waves at a frequency of 835 MHz. What is the wavelength of these waves?

A)0.0146 m
B)0.359 m
C)0.842 m
D)1.62 m
E)2.47 m

Question 21

Linearly polarized light is incident of a sheet of polarizing material. The angle between the transmission axis and the incident electric field is 44°. What percentage of the incident intensity is transmitted?

A)38 %
B)43 %
C)52 %
D)72 %
E)84 %

Question 22

An incandescent light bulb radiates uniformly in all directions with a total average power of 1.0 × 10² W. What is the maximum value of the magnetic field at a distance of 0.50 m from the bulb?

A)8.4 × 10^-7 T
B)5.2 × 10^-7 T
C)3.1 × 10^-7 T
D)1.6 × 10^-7 T
E)zero tesla

Question 23

A linearly polarized beam of light is incident upon a group of three polarizing sheets which are arranged so that the transmission axis of each sheet is rotated by 45° with respect to the preceding sheet as shown. What fraction of the incident intensity is transmitted?

A)1/8
B)1/4
C)3/8
D)1/2
E)3/4

Question 24

Two polarizing sheets have their transmission axes parallel so that the intensity of unpolarized light transmitted through both of them is a maximum. Through what angle must either sheet be rotated if the transmitted intensity is 25 % of the incident intensity?

A)15°
B)30°
C)45°
D)60°
E)75°

Question 25

The peak value of the electric field component of an electromagnetic wave is E. At a particular instant, the intensity of the wave is of 0.020 W/m². If the electric field were increased to 5E, what would be the intensity of the wave?

A)0.020 W/m²
B)0.10 W/m²
C)0.25 W/m²
D)0.50 W/m²
E)1.0 W/m²

Question 26

Light emerges from a polarizer that has its transmission axis located along the x axis. The light then passes through two additional sheets of polarizing material. It is desired to orient the two sheets so that, after passing through both of them, the electromagnetic wave has the maximum possible intensity and is polarized 90° with respect to the x axis. How should the transmission axes of the sheets be oriented? Note: the following answers give the angles that the transmission axes make with respect to the x axis.

A)
B)
C)
D)
E)

Question 27

The amplitude of the electric field component of an electromagnetic wave is increased from E to 3E. What is the corresponding change in the intensity of the wave?

A)The intensity is unchanged by the increase in E.
B)The intensity increases by a factor of nine.
C)The intensity increases by a factor of three.
D)The intensity decreases by a factor of three.
E)The intensity decreases by a factor of nine.

Question 28

The magnitude of the magnetic field component of a plane polarized electromagnetic wave traveling in vacuum is given by B_y = B_o sin[k z - $\omega$ t]. Which one of the following statements concerning this electromagnetic wave is true?

A)The wavelength is equal to k/ $\omega$ .
B)The wave propagates in the y direction.
C)The wave is polarized in the x direction.
D)The electric field component vibrates in the z direction.
E)The electric field component has a magnitude of E = cB_o cos[k z - $\omega$ t].

Question 29

An electromagnetic wave has an electric field with peak value 250.0 N/C. What is the average energy delivered to a surface with area 0.75 m² by this wave in one hour?

A)8.3 × 10⁴ J
B)1.6 × 10⁵ J166 J
C)2.2 × 10⁵ J
D)3700 J
E)9960 J

Question 30

A laser uniformly illuminates an area with green light that has an average intensity of 550 W/m². What is the rms value of the electric field of this light?

A)322 N/C
B)405 N/C
C)455 N/C
D)643 N/C
E)891 N/C

Question 31

Electromagnetic waves are radiated uniformly in all directions from a source. The rms electric field of the waves is measured 35 km from the source to have an rms value of 0.012 N/C. Determine the average total power radiated by the source.

A)5.9 × 10³ W
B)9.0 × 10³ W
C)2.4 × 10⁴ W
D)6.3 × 10⁴ W
E)1.6 × 10⁵ W

Question 32

An astronomer observes electromagnetic waves emitted by oxygen atoms in a distant galaxy that have a frequency of 5.710 × 10¹⁴ Hz. In the laboratory on earth, oxygen atoms emit waves that have a frequency of 5.841 × 10¹⁴ Hz. Determine the relative velocity of the galaxy with respect to the astronomer on the earth. Note: The speed of light is 2.9979 × 10⁸ m/s.

A)6.724 × 10⁶ m/s, away from earth
B)6.724 × 10⁶ m/s, toward earth
C)2.931 × 10⁸ m/s, away from earth
D)4.369 × 10⁴ m/s, toward earth
E)4.369 × 10⁴ m/s, away from earth

Question 33

Unpolarized light with an average intensity of 845 W/m² enters a polarizer with a vertical transmission axis. The transmitted light then enters a second polarizer. The light that exits the second polarizer is found to have an average intensity of 225 W/m². What is the orientation angle of the second polarizer relative to the first one?

A)54.7°
B)22.6°
C)43.1°
D)77.3°
E)zero degrees

Question 34

What would the speed of an observer be if a red (4.688 × 10¹⁴ Hz) traffic light appeared green (5.555 × 10¹⁴ Hz) to the observer?

A)4.445 × 10⁸ m/s
B)2.219 × 10⁸ m/s
C)8.438 × 10⁷ m/s
D)5.548 × 10⁷ m/s
E)2.890 × 10⁶ m/s

Question 35

An electromagnetic wave has an electric field with a peak value of 250 N/C. What is the average intensity of the wave?

A)0.66 W/m²
B)0.89 W/m²
C)83 W/m²
D)120 W/m²
E)170 W/m²

Question 36

Unpolarized light of intensity S₀ passes through two sheets of polarizing material whose transmission axes make an angle of 60° with each other as shown in the figure. What is the intensity of the transmitted beam, S_T?

A)S₀/4
B)S₀/8
C)3S₀/4
D)S₀/16
E)zero

Question 37

A local radio station transmits radio waves uniformly in all directions with a total power of 7.50 × 10⁴ W. What is the intensity of these waves when they reach a receiving antenna located 20.0 km from the transmitting antenna?

A)1.49 × 10^-5 W/m²
B)5.96 × 10^-5 W/m²
C)3.73 × 10^-6 W/m²
D)1.17 × 10^-7 W/m²
E)5.60 × 10^-8 W/m²

Question 38

The most convincing evidence that electromagnetic waves are transverse waves is that

A)they can be polarized.
B)they carry energy through space.
C)they can travel through a material substance.
D)they do not require a physical medium for propagation.
E)all electromagnetic waves travel with the same speed through vacuum.

Question 39

Which one of the following statements concerning the energy carried by an electromagnetic wave is true?

A)The energy is carried only by the electric field.
B)More energy is carried by the electric field than by the magnetic field.
C)The energy is carried equally by the electric and magnetic fields.
D)More energy is carried by the magnetic field than by the electric field.
E)The energy is carried only by the magnetic field.

Question 40

A minivan moving at 38 m/s passes an unmarked state police car moving at 24 m/s. The electromagnetic waves produced by the radar gun in the police car have a frequency of 8.25 × 10⁹ Hz. What is the magnitude of the difference in frequency between the waves emitted by the gun and those that are reflected back from the speeding minivan?

A)180 Hz
B)390 Hz
C)770 Hz
D)1440 Hz
E)2100 Hz

Question 41

The electromagnetic wave of the radiation field from a wire antenna travels toward the plane of your paper (which is in the -z direction). At time t = 0 s, the wave strikes your paper at normal incidence. The magnetic field vector at point O in the figure points in the -y direction and has a magnitude of 4.0 × 10^-8 T. The frequency of the wave is 1.0 × 10¹⁶ Hz.
What is the magnitude of the magnetic field at point O at time t = 5.0 × 10^-17 s?

A)1.0 × 10-8 T
B)2.0 × 10-8 T
C)3.0 × 10-8 T
D)4.0 × 10-8 T
E)5.0 × 10-8 T

Question 42

Linearly polarized light is incident upon a polarizing sheet that has a transmission axis is parallel to the incident light. The sheet is rotated about its axis through 360° (one complete revolution). At how many positions, including the initial and final positions, will the transmitted intensity be a maximum?

A)6
B)5
C)4
D)3
E)2

Question 43

The electromagnetic wave of the radiation field from a wire antenna travels toward the plane of your paper (which is in the -z direction). At time t = 0 s, the wave strikes your paper at normal incidence. The magnetic field vector at point O in the figure points in the -y direction and has a magnitude of 4.0 × 10^-8 T. The frequency of the wave is 1.0 × 10¹⁶ Hz.
What is the direction of polarization of this electromagnetic wave?

A)the x direction
B)the y direction
C)the z direction
D)45° with respect to the x direction
E)the wave is not polarized

Question 44

The figure shows the time variation of the magnitude of the electric field of an electromagnetic wave produced by a wire antenna.
What is the rms value of the magnitude of the magnetic field?

A)1.4 × 10^-8 T
B)2.4 × 10^-8 T
C)3.3 × 10^-8 T
D)4.6 × 10^-8 T
E)5.4 × 10^-8 T

Question 45

The electromagnetic wave of the radiation field from a wire antenna travels toward the plane of your paper (which is in the -z direction). At time t = 0 s, the wave strikes your paper at normal incidence. The magnetic field vector at point O in the figure points in the -y direction and has a magnitude of 4.0 × 10^-8 T. The frequency of the wave is 1.0 × 10¹⁶ Hz.
What is the intensity of the electromagnetic wave at time t = 0 s?

A)0.24 W/m²
B)0.38 W/m²
C)0.48 W/m²
D)0.76 W/m²
E)24 W/m²

Question 46

A linearly polarized electromagnetic wave is sent through two sheets of polarizing material. The first sheet, A, is oriented so that its transmission axis makes an angle of 30° with respect to the incident electric field of the wave. The second sheet, B, is oriented so that its transmission axis makes an angle of 90° with the incident electric field of the wave. The incident beam has an electric field of peak magnitude E₀ and average intensity S₀.
What is the average intensity of the wave after it passes through B?

A)0.19S₀
B)0.34S₀
C)0.43S₀
D)0.50S₀
E)zero

Question 47

The electromagnetic wave of the radiation field from a wire antenna travels toward the plane of your paper (which is in the -z direction). At time t = 0 s, the wave strikes your paper at normal incidence. The magnetic field vector at point O in the figure points in the -y direction and has a magnitude of 4.0 × 10^-8 T. The frequency of the wave is 1.0 × 10¹⁶ Hz.
What is the magnitude of the associated electric field at time t = 0 s?

A)7.5 × 10^-3 N/C
B)1.3 N/C
C)7.5 N/C
D)12 N/C
E)7.5 × 10⁴ N/C

Question 48

The electromagnetic wave of the radiation field from a wire antenna travels toward the plane of your paper (which is in the -z direction). At time t = 0 s, the wave strikes your paper at normal incidence. The magnetic field vector at point O in the figure points in the -y direction and has a magnitude of 4.0 × 10^-8 T. The frequency of the wave is 1.0 × 10¹⁶ Hz.
What is the rms value of the electric field? Assume that the figure shows the peak value of .

A)7.5 N/C
B)8.5 N/C
C)17 N/C
D)1.1 × 10⁴ N/C
E)8.5 × 10^-3 N/C

Question 49

The electromagnetic wave of the radiation field from a wire antenna travels toward the plane of your paper (which is in the -z direction). At time t = 0 s, the wave strikes your paper at normal incidence. The magnetic field vector at point O in the figure points in the -y direction and has a magnitude of 4.0 × 10^-8 T. The frequency of the wave is 1.0 × 10¹⁶ Hz.
What is the direction of the electric field?

A)It points in the negative y direction.
B)It points in the positive y direction.
C)It points in the negative z direction.
D)It points in the negative x direction.
E)It points in the positive x direction.

Question 50

The electromagnetic wave of the radiation field from a wire antenna travels toward the plane of your paper (which is in the -z direction). At time t = 0 s, the wave strikes your paper at normal incidence. The magnetic field vector at point O in the figure points in the -y direction and has a magnitude of 4.0 × 10^-8 T. The frequency of the wave is 1.0 × 10¹⁶ Hz.
What is the wavelength of this electromagnetic wave?

A)0.33 nm
B)3.3 nm
C)20 nm
D)30 nm
E)40 nm

Question 51

The figure shows the time variation of the magnitude of the electric field of an electromagnetic wave produced by a wire antenna.
Determine the wavelength of the wave.

A)0.30 m
B)0.60 m
C)0.79 m
D)1.2 m
E)2.3 m

Question 52

The figure shows the time variation of the magnitude of the electric field of an electromagnetic wave produced by a wire antenna.
Determine the rms value of the electric field magnitude.

A)7.1 N/C
B)12 N/C
C)14 N/C
D)19 N/C
E)28 N/C

Question 53

The figure shows the time variation of the magnitude of the electric field of an electromagnetic wave produced by a wire antenna.
Determine the frequency of the wave.

A)1.0 × 10⁹ Hz
B)1.3 × 10⁸ Hz
C)2.5 × 10⁸ Hz
D)3.8 × 10⁸ Hz
E)5.0 × 10⁸ Hz

Question 54

The electromagnetic wave of the radiation field from a wire antenna travels toward the plane of your paper (which is in the -z direction). At time t = 0 s, the wave strikes your paper at normal incidence. The magnetic field vector at point O in the figure points in the -y direction and has a magnitude of 4.0 × 10^-8 T. The frequency of the wave is 1.0 × 10¹⁶ Hz.
What is the direction of electromagnetic energy transport?

A)the positive x direction
B)the negative x direction
C)the positive y direction
D)the negative y direction
E)the negative z direction

Question 55

The figure shows the time variation of the magnitude of the electric field of an electromagnetic wave produced by a wire antenna.
What is the peak value of the magnetic field?

A)1.4 × 10^-8 T
B)2.3 × 10^-8 T
C)3.3 × 10^-8 T
D)4.6 × 10^-8 T
E)5.4 × 10^-8 T

Question 56

The electromagnetic wave of the radiation field from a wire antenna travels toward the plane of your paper (which is in the -z direction). At time t = 0 s, the wave strikes your paper at normal incidence. The magnetic field vector at point O in the figure points in the -y direction and has a magnitude of 4.0 × 10^-8 T. The frequency of the wave is 1.0 × 10¹⁶ Hz.
What is the rms value of the magnetic field? Assume that the figure shows the peak value of .

A)1.0 × 10^-8 T
B)1.4 × 10^-8 T
C)2.8 × 10^-8 T
D)4.6 × 10^-8 T
E)5.7 × 10^-8 T

Question 57

A linearly polarized electromagnetic wave is sent through two sheets of polarizing material. The first sheet, A, is oriented so that its transmission axis makes an angle of 30° with respect to the incident electric field of the wave. The second sheet, B, is oriented so that its transmission axis makes an angle of 90° with the incident electric field of the wave. The incident beam has an electric field of peak magnitude E₀ and average intensity S₀.
What is the average intensity of the wave after it passes through A?

A)0.30S₀
B)0.50S₀
C)0.60S₀
D)0.75S₀
E)0.87S₀

Question 58

A linearly polarized electromagnetic wave is sent through two sheets of polarizing material. The first sheet, A, is oriented so that its transmission axis makes an angle of 30° with respect to the incident electric field of the wave. The second sheet, B, is oriented so that its transmission axis makes an angle of 90° with the incident electric field of the wave. The incident beam has an electric field of peak magnitude E₀ and average intensity S₀.
What is the peak value of the electric field amplitude after it goes through sheet A?

A)0.30E₀
B)0.50E₀
C)0.60E₀
D)0.75E₀
E)0.87E₀

Question 59

An FM radio station emits an electromagnetic wave which is received by a circuit containing a 3.33 × 10^-7 H inductor and a variable capacitor set at 7.31 × 10^-12 F. What is the frequency of the radio wave?

A)1.02 × 10⁸ Hz
B)8.80 × 10⁷ Hz
C)1.58 × 10⁸ Hz
D)9.40 × 10⁷ Hz
E)9.80 × 10⁷ Hz

Question 60

A linearly polarized electromagnetic wave is sent through two sheets of polarizing material. The first sheet, A, is oriented so that its transmission axis makes an angle of 30° with respect to the incident electric field of the wave. The second sheet, B, is oriented so that its transmission axis makes an angle of 90° with the incident electric field of the wave. The incident beam has an electric field of peak magnitude E₀ and average intensity S₀.
Suppose that A and B are interchanged so that the wave is first incident upon B. What is the average wave intensity after passing through both polarizing sheets?

A)0.19S₀
B)0.34S₀
C)0.43S₀
D)0.50S₀
E)zero

Question 61

The figure shows the time variation of the magnitude of the electric field of an electromagnetic wave produced by a wire antenna.
What is the magnitude of the electric field at t = 3.34 × 10^-10 s?

A)2.0 N/C
B)5.0 N/C
C)7.1 N/C
D)10.0 N/C
E)zero N/C

Question 62

The figure shows the time variation of the magnitude of the electric field of an electromagnetic wave produced by a wire antenna.
What is the average intensity of this electromagnetic wave?

A)0.13 W/m²
B)0.26 W/m²
C)0.33 W/m²
D)0.36 W/m²
E)0.54 W/m²

Question 63

The figure shows the time variation of the magnitude of the electric field of an electromagnetic wave produced by a wire antenna.
To which region of the electromagnetic spectrum does this wave belong?

A)X-rays
B)gamma rays
C)visible light
D)infrared radiation
E)radio waves

Question 64

The figure shows the time variation of the magnitude of the electric field of an electromagnetic wave produced by a wire antenna.
What is the average total energy density of this electromagnetic wave?

A)6.2 × 10^-11 J/m³
B)8.6 × 10^-11 J/m³
C)1.1 × 10^-10 J/m³
D)1.8 × 10^-10 J/m³
E)4.4 × 10^-10 J/m³

Question 65

The figure shows the time variation of the magnitude of the electric field of an electromagnetic wave produced by a wire antenna.
What is the magnitude of the magnetic field at t = 6.67 × 10^-10 s?

A)1.7 × 10^-8 T
B)2.3 × 10^-8 T
C)2.9 × 10^-8 T
D)3.3 × 10^-8 T
E)zero tesla

Question 66

The figure shows the time variation of the magnitude of the electric field of an electromagnetic wave produced by a wire antenna.
What is the magnitude of the magnetic field at t = 6.0 × 10^-9 s?

A)1.7 × 10^-8 T
B)2.3 × 10^-8 T
C)2.8 × 10^-8 T
D)3.3 × 10^-8 T
E)zero tesla