Chapter 22 Full Test Bank Electromagnetic Waves

Physics, 9e (Giambattista)

Chapter 22 Electromagnetic Waves

1) Your favorite radio station is located due north of your house and broadcasts using a horizontal electric dipole antenna directed north-south. To receive this signal you need to

A) move to a town that is farther to the east or west.

B) use a magnetic dipole antenna instead of an electric dipole antenna.

C) orient the receiving antenna horizontally north-south.

D) use a vertical receiving antenna.

2) A dipole radio transmitter has its rod-shaped antenna oriented vertically. At a point due south of the transmitter, the radio waves have their magnetic field

A) oriented in any horizontal direction.

B) oriented east-west.

C) oriented vertically.

D) oriented north-south.

3) The electromagnetic spectrum arranged by increasing wavelength is

A) radio waves, gamma rays, x-rays, visible light, infrared, microwave, ultraviolet.

B) x-rays, gamma rays, ultraviolet, visible light, infrared, microwave, radio waves.

C) infrared, gamma rays, x-rays, ultraviolet, visible light, microwave, radio waves.

D) gamma rays, x-rays, ultraviolet, visible light, infrared, microwave, radio waves.

4) Electromagnetic waves of wavelength 1000 nm are classified as

A) radio waves.

B) microwaves.

C) infrared.

D) x-rays.

E) gamma rays.

5) An electromagnetic wave with a wavelength about the same as the diameter of an apple would be

A) an x-ray.

B) UV.

C) infrared.

D) a microwave.

E) a radio wave.

6) Wavelengths just shorter than visible light are classified as

A) gamma rays.

B) x-rays.

C) microwaves.

D) ultraviolet.

E) radio waves.

7) What color would an EM wave with a frequency of 430 THz be?

A) blue

B) green

C) yellow

D) red

E) not in the visible range

8) The longest wavelengths of visible light are in the color

A) red.

B) orange.

C) green.

D) blue.

E) violet.

9) The highest frequency in visible light is associated with the color

A) red.

B) orange.

C) green.

D) blue.

E) violet.

10) The wavelengths associated with thermal radiation at everyday temperatures are in which spectral region?

A) infrared

B) ultraviolet

C) shorter visual

D) longer visual

E) x-ray

11) In what spectral range are black lights that cause materials to fluoresce in the visible?

A) x-ray

B) infrared

C) ultraviolet

D) radio

E) microwave

12) Electromagnetic wavelengths of a few centimeters are classified as what type of radiation?

A) visible light

B) ultraviolet

C) microwaves

D) radio waves

E) gamma rays

13) The background radiation in space corresponds to blackbody radiation of what temperature?

A) 0 K

B) 2.7 K

C) 273 K

D) 5800 K

E) 98.6°F

14) Radio waves were discovered by

A) Hertz.

B) Maxwell.

C) Penzias.

D) Dumont.

E) Marconi.

15) Light of 10 cm wavelength is classified as what type of radiation?

A) gamma ray

B) x-ray

C) UV

D) microwave

E) visible

16) Light of wavelength 600 nm in air enters a medium in which the index of refraction is 1.73. What is the frequency of this light in the medium?

A) 5.00 × 1014 Hz

B) 2.89 × 1014 Hz

C) 8.65 × 1014 Hz

D) 3.46 × 1014 Hz

E) 1.04 × 1014 Hz

17) εo μo = ?

A) c

B) c2

C) c−1

D) c−2

E) c½

18) An electromagnetic wave is created by

A) an electrical charge moving at a certain velocity.

B) all electric charges.

C) a magnet moving with a certain velocity.

D) an accelerating electric charge.

19) How long does it take for a radio signal to travel to a spacecraft 1.5 × 1011 m away?

A) 5.0 s

B) 50 s

C) 5.0 × 102 s

D) 5.0 × 103 s

E) 1.0 × 103 s

20) What is a light-year in SI units?

A) 3.0 × 1015 m

B) 9.5 × 1015 m

C) 3.0 × 1011 m

D) 1.1 × 1011 m

E) 4.5 × 1037 m

21) What is the speed of light in a material that has an index of refraction of 2.0?

A) 6.0 × 108 m/s

B) 1.5 × 108 m/s

C) 2.0 × 108 m/s

D) 5.0 × 108 m/s

E) No such index can exist.

22) When light passes from one medium into another with a different index of refraction, which of the following does or do NOT change?

A) the speed

B) the wavelength

C) the frequency

D) the speed and the wavelength

E) the frequency and the wavelength

23) If light has a wavelength of 600 nm in a vacuum, what is its wavelength in a material with an index of refraction of 1.50?

A) 600 nm

B) 900 nm

C) 400 nm

D) 1.35 × 103 nm

E) 267 nm

24) Household wiring can emit electromagnetic waves of frequency 60 Hz. What is the wavelength of these waves?

A) 5.0 × 102 m

B) 5.0 × 103 m

C) 5.0 × 104 m

D) 5.0 × 105 m

E) 5.0 × 106 m

25) What is the wavelength from a radio station having frequency 108 MHz?

A) 2.78 m

B) 27.8 m

C) 32.3 m

D) 323 m

E) 108 m

26) The Sun is 1.50 × 108 km from the Earth. How long does it take for light to reach us from the Sun?

A) 2.00 ms

B) 2.00 s

C) 0.50 s

D) 8.33 min

E) almost instantaneous

27) Approximately how long does it take for light to travel one foot?

A) 1 ms

B) 1 μs

C) 1 ns

D) 1 ps

E) 1 fs

28) What index of refraction halves the wavelength that light has in a vacuum?

A) 1.33

B) 1.50

C) 1.41

D) 2.00

E) 5.00

29) How far does light travel in a century?

A) 9.5 × 1020 m

B) 9.5 × 1017 m

C) 9.5 × 1015 m

D) 9.5 × 1014 m

E) 9.5 × 1012 m

30) If the wavelength of light is 400 nm in a substance where the speed of light is 2.35 × 108 m/s, what is the wavelength of this light in air?

A) 313 nm

B) 400 nm

C) 511 nm

D) 635 nm

E) 940 nm

31) Light passes from medium one (v1) to medium two (v2). If v1 < v2 then at the boundary

A) f increases, λ decreases.

B) f does not change, λ increases.

C) f decreases, λ increases.

D) f does not change, λ decreases.

32) The speed of an electromagnetic wave in vacuum depends on

A) the amplitude of the electric and magnetic fields.

B) the frequency of the wavelength.

C) the angle between the electric and magnetic fields.

D) none of these choices are correct.

33) Which of the following is the direction of an electromagnetic wave having electric and magnetic field vectors E and B?

A) E

B) B

C) E + B

D) E × B

E) B × E

34) What is the wave number for a wavelength of 600 nm?

A) 600 nm

B) 1.67 × 106 m−1

C) 1.05 × 107 m−1

D) 9.55 × 10−8 m

E) 9.55 × 10−8 m−1

35) In vacuum, the components of an EM wave are Ey = (50 V/m) cos [(5.00 m−1)x + ωt], Ex = 0, and Ez = 0. In what direction is this wave moving?

A) positive x-direction

B) negative x-direction

C) positive y-direction

D) negative y-direction

E) positive or negative z-direction

36) In vacuum, the components of an EM wave are Ey = (50 V/m) cos [(5.00 m−1)x + ωt], Ex = 0, and Ez = 0. What is the wavelength of the wave?

A) 5.00 m

B) 0.200 m

C) 1.26 m

D) 2.52 m

E) 0.796 m

37) In vacuum, the components of an EM wave are Ey = (50 V/m) cos [(5.00 m−1)x + ωt], Ex = 0, and Ez = 0. What is ω?

A) 1.50 × 109 rad/s

B) l.20 × 109 rad/s

C) 1.00 × 109 rad/s

D) 8.00 × 108 rad/s

E) More information is needed.

38) In vacuum, the components of an EM wave are Ey = (50 V/m) cos [(5.0 m−1)x + ωt], Ex = 0, and Ez = 0. What is the amplitude of the magnetic field for this wave?

A) 5.00 × 10−7 T

B) 1.67 × 10−7 T

C) 2.00 × 10−7 T

D) 1.50 × 10−6 T

E) 1.33 × 10−6 T

39) At a distance of 10 m from a light bulb, the rms value of the electric field is 16 V/m. What is the rms value of the electric field at a distance of 20 m from the light bulb?

A) 32 V/m

B) 16 V/m

C) 8.0 V/m

D) 4.0 V/m

E) 2.0 V/m

40) If the rms value of the electric field is 9.0 V/m at a distance of 6.0 m from an isotropic source, what is the rms value of the magnetic field at a distance of 12 m from the source?

A) 3.0 × 10−8 T

B) 1.5 × 10−8 T

C) 0.75 × 10−8 T

D) 0.38 × 10−8 T

E) 0.19 × 10−8 T

41) If the intensity of radiation from the Sun is 1.4 kW/m2 at a distance of 150 × 106 km, at what distance is the intensity 5.6 kW/m2?

A) 300 × 106 km

B) 100 × 106 km

C) 75 × 106 km

D) 38 × 106 km

E) less than 30 × 106 km

42) If a 20 W laser beam, which has an initial diameter of 2.0 mm, spreads out to a diameter of 2.0 m after traveling 10,000 m, what is the final intensity of the beam?

A) 20 × 10−4 W/m2

B) 20 × 10−6 W/m2

C) 20 × 10−8 W/m2

D) 6.4 W/m2

E) 6.4 × 10−6 W/m2

43) A 20 W laser beam, with an initial diameter of 2.0 mm, spreads out to a diameter of 2.0 m after traveling 10,000 m. What is the initial intensity of the beam?

A) 20 × 106 W/m2

B) 6.4 × 106 W/m2

C) 3.2 × 106 W/m2

D) 2.0 × 105 W/m2

E) 1.0 × 105 W/m2

44) A 20 W laser beam, with an initial diameter of 2.0 mm, spreads out to a diameter of 2.0 m after traveling 10,000 m. What is the initial Erms of the beam?

A) 4.9 × 104 V/m

B) 2.5 × 103 V/m

C) 1.2 × 103 V/m

D) 1.9 × 102 V/m

E) 1.7 × 102 V/m

45) What is the intensity of the electromagnetic radiation 2.00 m from a 100 W isotropic source?

A) 25.0 W/m2

B) 6.25 W/m2

C) 4.00 W/m2

D) 1.99 W/m2

E) 1.00 W/m2

46) For electromagnetic radiation of intensity of 1.00 W/m2, what is the rms value of the electric field?

A) 19.4 V/m

B) 9.69 V/m

C) 6.45 × 10-8 V/m

D) 9.11 × 10-8 V/m

E) 3.00 × 107 V/m

47) Radiation of intensity 1.00 kW/m2 is incident on an area perpendicular to the incoming light. The area is now rotated 20° about an axis perpendicular to the incoming light. What is the resulting power per unit area now reaching the surface?

A) 1.00 kW/m2

B) 0.940 kW/m2

C) 0.880 kW/m2

D) 0.800 kW/m2

E) 0.340 kW/m2

48) At the summer solstice in June, at what latitude is the Sun directly overhead at solar noon?

A) 0.0° (the equator)

B) 23.5° N

C) 23.5° S

D) 66.5° N

E) 40.0° N

49) The direction of polarization of an electromagnetic wave is taken by convention to be

A) the electric field direction.

B) the magnetic field direction.

C) the direction of E × B.

D) perpendicular to the electric field direction.

E) None of these choices are correct.

50) Randomly polarized light of intensity I0 is passed through two polarizers whose transmission axes differ by 45°. What is the intensity of the light that has passed through both polarizers?

A) 0.70 I0

B) 0.50 I0

C) 0.35 I0

D) 0.25 I0

E) 0.00

51) Plane-polarized light of intensity I0 is passed through a polarizer oriented at 45° to the original plane of polarization. What is the intensity transmitted?

A) 0.70 I0

B) 0.50 I0

C) 0.35 I0

D) 0.25 I0

E) 0.00

52) Plane-polarized light of intensity I0 is passed through two polarizers, the first one at 45° to the original polarization direction and the second rotated an additional 45° so that it is perpendicular to the original polarization. What intensity is transmitted?

A) 0.50 I0

B) 0.35 I0

C) 0.25 I0

D) 0.13 I0

E) 0

53) Unpolarized light of intensity I0 is sent through an arrangement of 4 polarizers. Each polarizer (after the first) is rotated 30° relative to the preceding one, so that the last polarizer is perpendicular to the first. What is the intensity transmitted by this system?

A) 0.75 I0

B) 0.50 I0

C) 0.42 I0

D) 0.21 I0

E) 0

54) Plane-polarized light of intensity I0 is sent through two polarizers, the first of which is rotated 45° clockwise relative to the original polarization, while the second is rotated 45° counterclockwise relative to the original polarization. What is the transmitted intensity?

A) 0.71 I0

B) 0.50 I0

C) 0.35 I0

D) 0.25 I0

E) 0

55) If unpolarized light with Erms = 20 V/m is passed through a polarizer, what is the transmitted Erms?

A) 20 V/m

B) 14 V/m

C) 10 V/m

D) 7.1 V/m

E) 5.0 V/m

56) If you are facing north with the Sun directly overhead, the light coming to your eyes from the sky just above the horizon is

A) partially polarized east-west.

B) partially polarized north-south.

C) randomly polarized.

D) partially polarized up-down.

57) Light from an astronomical source is found to be shifted to a frequency one percent lower than had the source been at rest. What relative velocity could cause such a shift?

A) 3.0 × 107 m/s moving away from the observer

B) 3.0 × 106 m/s moving away from the observer

C) 3.0 × 106 m/s moving toward the observer

D) 1.5 × 106 m/s moving toward the observer

E) 1.5 × 106 m/s moving away from the observer

58) Using the approximate formula for the Doppler shift, fo ≈ fs (1 + vrel/c) one finds that a source is moving away at 0.60 c. What result would the exact formula yield for the recession speed?

A) 0.84 c

B) 0.72 c

C) 0.60 c

D) 0.54 c

E) 0.40 c

59) Light of wavelength 661.1 nm is received from a star that is emitting light of wavelength 659.6 nm. How fast is the star moving relative to the Earth, and is it moving toward or away?

A) 580 km/s away

B) 580 km/s toward

C) 680 km/s away

D) 680 km/s toward

60) How fast would you have to drive in order to see a red light as green? Assume λ = 630 nm for red and λ = 530 nm for green.

A) 5 × 107 m/s

B) 5 × 106 m/s

C) 5 × 105 m/s

D) 5 × 104 m/s

61) A distant star emits light of wavelength 620 nm. As measured by an Earth observer, the light is shifted to 635 nm. Assuming the star is moving either away (positive radial velocity) or toward (negative radial velocity) Earth, what is its radial velocity relative to Earth? 

A) −0.11c

B) −0.024c

C) 0.11c

D) 0.024c

62) It is possible to detect Doppler shifts in the light emitted from each side of a rapidly spinning star. Suppose the light from a nearby star of radius 2.5 × 108 km is blue-shifted on one side of the star and red-shifted on the other side. Assume the center of mass of the star is stationary relative to Earth. If the star emits light of wavelength 525 nm that is shifted, in the received light, to 523 nm on one side of the star and to 527 nm on the other side, what is the rotational period of the star?

A) 34 days

B) 32 days

C) 24 days

D) 16 days

63) It is possible to detect Doppler shifts in the light emitted from each side of a rapidly spinning star. Suppose the light from a nearby star of radius 2.5 × 108 km is blue-shifted on one side of the star and red-shifted on the other side. Assume the center of mass of the star is stationary relative to Earth. If the rotational period of the star is 72 h and the star emits (unshifted) light of wavelength 525 nm, what is the wavelength of the light received on Earth from the side of the star rotating toward us? 

A) 536 nm

B) 504 nm

C) 530 nm

D) 520 nm

E) 546 nm

F) 514 nm

64) A distant star emits light with a peak intensity at 620 nm. If the star is moving toward Earth at 0.024c, what is the wavelength of the peak intensity as measured by an Earth observer?

A) 605 nm

B) 591 nm

C) 650 nm

D) 635 nm

65) The Sun has a radius of 6.955 × 108 km and a rotational period of 25.38 days. What is the difference in the wavelength of the peak of the observed spectrum between light received from the approaching side of the Sun and from the receding side of the Sun? Observations of the middle of the Sun place the spectral peak at 480 nm.

A) 13 nm

B) 6.4 nm

C) 1.6 nm

D) 3.2 nm

66) Nexrad radar uses electromagnetic radiation of frequency of 2.7 GHz to measure the speed of cloud systems. Radio waves from a transmitter are sent outward toward a cloud system, and the waves are reflected back toward the source. If the cloud system is moving, the reflected waves will be Doppler shifted. Suppose a Nexrad system observes clouds moving toward the transmitter at 21 m/s. What is the difference between the transmitted and received frequencies of the radar in this case?

A) 380 Hz

B) 760 Hz

C) 570 Hz

D) 190 Hz

67) The rms electric field strength at a distance r from a 25 W light source is found to be 4.33 N/C. What is the distance r?

A) 22 m

B) 6.3 m

C) 30 m

D) 40 m

68) You wish to read by the light of a lamp with a single lightbulb at your desk. In order to get the same brightness on the page from a 25 W bulb as you can from 100 W bulb, how much closer do you need to bring the lamp to your book? Assume that the light bulbs are equally efficient.

A) 1/2 the distance

B) 1/8 the distance

C) 1/4 the distance

D) 1/16 the distance

69) At the Earth's orbital distance from the Sun, the intensity of solar radiation is approximately 1400 W/m2. What is the intensity at Mercury's orbital distance, which is 38.7% that of Earth?

A) 2280 W/m2

B) 3800 W/m2

C) 9300 W/m2

D) 540 W/m2

70) At the Earth's orbital distance from the Sun, the intensity of solar radiation is approximately 1400 W/m2. What is the rms electric field?

A) 726 V/m

B) 363 kV/m

C) 527 kV/m

D) 513 kV/m

71) What total power is radiated by a light bulb that provides 12 mW on a 15 cm × 25 cm sheet of paper, which is 1.7 m from the bulb? Assume that the paper is oriented with its surface perpendicular to the light rays.

A) 2.9 W

B) 12 W

C) 1.7 W

D) 6.6 W

72) At the Earth's surface, the intensity of solar radiation is approximately 1000 W/m2. At a latitude of 44.5 degrees north, when the Sun is highest in the sky on the winter solstice, the Sun's rays are incident at an angle of 68.0 degrees from the vertical. What power is incident upon a 1.00 m × 1.50 m window in a vertical, south-facing wall at this time?

A) 1390 W

B) 927 W

C) 562 W

D) 375 W

73) At the Earth's surface, the intensity of solar radiation is approximately 1000 W/m2. If 1390 W are incident upon a 1.0 m × 1.5 m window in a vertical, south-facing wall, what is the angle with respect to the vertical of the Sun's rays?

A) 61°

B) 68°

C) 44°

D) 46°

E) 22°

F) 29°

74) A radio station utilizes a horizontal electric dipole antenna directed north-south as a transmitter. You are located due west of the station and wish to use a magnetic dipole antenna to receive the broadcast. What should the orientation of your antenna be? 

A) axis horizontal east-west

B) axis horizontal in any direction

C) axis horizontal north-south

D) Unable to answer given the information.

E) axis vertical

75) In an unpolarized EM wave, the electric field direction is

A) perpendicular to the magnetic field direction

B) parallel to the magnetic field direction.

C) perpendicular to the direction of wave propagation, but randomly oriented with respect to the magnetic field direction.

D) parallel to the direction of wave propagation.

76) If the distance from a point source of EM radiation is doubled, the intensity is

A) doubled

B) the same as it was before.

C) reduced by a factor of four.

D) increased by a factor of four.

E) cut in half.

77) A circularly polarized EM wave has an electric field magnitude 3.0 mV/m. If the wave passes through a polarizer, what will be the amplitude of the electric field in the transmitted wave?

A) 3.0 mV/m

B) 2.1 mV/m

C) 1.5 mV/m

D) 0

78) A circularly polarized EM wave with intensity I0 is incident on a polarizer. What is the intensity of the transmitted wave?

A) I0

B) 0.71 I0

C) 0.5 I0

D) 0

79) Light of intensity I0 passes through a polarizer at normal incidence and the intensity of the transmitted light is observed to be ½ I0. It is further found that the intensity does not change as the polarizer's transmission axis is rotated. Which of the following could be the polarization state of the incident light?

A) elliptical

B) linear

C) circular

D) unpolarized

E) more than one of the above

80) What is the smallest possible value for an index of refraction?

A) 0

B) 0.5

C) 1

D) just less than 1

E) (1/2)1/2