Question 1

What is the time required for laser light to travel to the Moon and back? The radius of the Moon's orbit = 3.84 * 108 m.

Accepted Answer

A) 2.56 s 
B) 0.13 s 
C) 8 min. 
D) 16 min. 
E) 23.1 s 
A) 2.56 s 
B) 0.13 s 
C) 8 min. 
D) 16 min. 
E) 23.1 s A

Question 2

Which waves have the shortest wavelength in the electromagnetic spectrum?

Accepted Answer

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

Question 3

An electromagnetic wave with maximum electric field Emax = 44.0 V/m propagates in the x direction as shown.What is the intensity of this wave (in W/m2)?

Accepted Answer

A) 2.01 
B) 2.27 
C) 2.57 
D) 2.90 
E) 3.28 
A) 2.01 
B) 2.27 
C) 2.57 
D) 2.90 
E) 3.28 C

Question 4

A beam of unpolarized light goes through 3 polarizers.The axes of polarization for each make a 0S1U1P1$\circ$S1S1P0,20S1U1P1$\circ$S1S1P0,and 40S1U1P1$\circ$S1S1P0 angle with the vertical,respectively.What percent of the incident light makes it through?

Accepted Answer

A) 11% 
B) 0% 
C) 39% 
D) 50% 
E) 78% 
A) 11% 
B) 0% 
C) 39% 
D) 50% 
E) 78%

Question 5

A radio transmission from a space probe passing by Pluto 4.6 * 1012 m away indicates a dangerous collision likely with one of Pluto's small moons.If the probe is moving at 19.4 km/s,how far will it move from the time it sent the message to Earth about its danger to the time at which it receives the command from Earth to start firing retro rockets?

Accepted Answer

A) 3.0 * 108 m 
B) 6.0 * 108 m 
C) 9.0 * 108 m 
D) None are correct. 
A) 3.0 * 108 m 
B) 6.0 * 108 m 
C) 9.0 * 108 m 
D) None are correct.

Question 6

What is the wavelength of the electromagnetic waves used for cell phone communications in the 850 MHz band?

Accepted Answer

A) 1.2 mm 
B) 12 cm 
C) 35 cm 
D) 1.4 m 
E) 2.8 m 
A) 1.2 mm 
B) 12 cm 
C) 35 cm 
D) 1.4 m 
E) 2.8 m

Question 7

Which waves have the smallest frequency in the electromagnetic spectrum?

Accepted Answer

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

Question 8

The intensity of polarized light decreases to 2/3 of the incident intensity after passing through a polarizing filter.The angle between the electric field and the polarization axis of the filter is

Accepted Answer

A) 54.7S1U1P1$\circ$S1S1P0. 
B) 35.3S1U1P1$\circ$S1S1P0. 
C) 29.1S1U1P1$\circ$S1S1P0. 
D) 25.0S1U1P1$\circ$S1S1P0. 
A) 54.7S1U1P1$\circ$S1S1P0. 
B) 35.3S1U1P1$\circ$S1S1P0. 
C) 29.1S1U1P1$\circ$S1S1P0. 
D) 25.0S1U1P1$\circ$S1S1P0.

Question 9

A 10-mW vertically polarized laser beam passes through a polarizing filter whose axis is 30 degrees from the horizontal.What is the power in the laser beam that emerges from the polarizer?

Accepted Answer

A) 8.7 mW 
B) 7.5 mW 
C) 5 mW 
D) 2.5 mW 
A) 8.7 mW 
B) 7.5 mW 
C) 5 mW 
D) 2.5 mW

Question 10

The invisible heat rays of sunlight appear next to what color in the visible spectrum when sunlight is sent through a prism?

Accepted Answer

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

Question 11

Which of the following exert the largest amount of radiation pressure?

Accepted Answer

A) a 1 mW laser pointer on a 2mm diameter spot 1 m away 
B) a 200 W light bulb on a 4mm diameter spot 10m away 
C) a 100 W light bulb on a 2 mm diameter spot 4 m away 
D) a 200 W light bulb on a 2 mm diameter spot 5 m away 
E) All of the choices exert the same pressure. 
A) a 1 mW laser pointer on a 2mm diameter spot 1 m away 
B) a 200 W light bulb on a 4mm diameter spot 10m away 
C) a 100 W light bulb on a 2 mm diameter spot 4 m away 
D) a 200 W light bulb on a 2 mm diameter spot 5 m away 
E) All of the choices exert the same pressure.

Question 12

In outer space,there are two astronauts at rest,one 20.0 m from the space shuttle and the other 40.0 m away from the shuttle.By using a laser,the astronaut located 40.0 m away from the shuttle decides to propel the other astronaut towards the space shuttle.He focuses the laser on a piece of totally reflecting fabric on her space suit.If her total mass with equipment is 100 kg and her resulting acceleration is 1.6 * 10-9 m/s2 towards the shuttle,what is the power of the laser?

Accepted Answer

A) 30 W 
B) 18 W 
C) 20 W 
D) 24 W 
E) 27 W 
A) 30 W 
B) 18 W 
C) 20 W 
D) 24 W 
E) 27 W

Question 13

An electric field has strength E = (65t - 22t2)V/m   in a region of space.What is the displacement current through a circular area of diameter 15 cm in the x-y plane in this region at t = 5.0s?

Accepted Answer

A) 97 pA 
B) 24 pA 
C) 180 pA 
D) 45 pA 
A) 97 pA 
B) 24 pA 
C) 180 pA 
D) 45 pA

Question 14

The response of the human eye peaks at around 550 nm (green).The frequency corresponding to the green light is

Accepted Answer

A) 3.64 * 1014 Hz. 
B) 4.29 * 1014 Hz. 
C) 5.46 * 1014 Hz. 
D) 7.50 * 1014 Hz. 
A) 3.64 * 1014 Hz. 
B) 4.29 * 1014 Hz. 
C) 5.46 * 1014 Hz. 
D) 7.50 * 1014 Hz.

Question 15

How long does it take for light to travel from the Sun to Earth? (Hint: the distance between Earth and Sun is 148 million km.)

Accepted Answer

A) less than 8 s 
B) about 8 s 
C) about 8 minutes 
D) about 8 hours 
E) more than 8 hours 
A) less than 8 s 
B) about 8 s 
C) about 8 minutes 
D) about 8 hours 
E) more than 8 hours

Question 16

An industrial CO2 laser produces a beam of radiation with average power of 5.00 kW at a wavelength of 10.6 $\mu$m.Such a laser can be used to cut steel up to 25 mm thick! The laser light is polarized in the x-direction,travels in the positive z-direction,and is collimated (neither diverging or converging)at a constant diameter of 120 $\mu$m.Calculate the amplitude of the oscillating magnetic field produced by the laser light.

Accepted Answer

A) 3.2 * 10-3 T 
B) 1.7 * 10-5 T 
C) 1.5 * 103 T 
D) 1.8 * 107 T 
E) 0.061 T 
A) 3.2 * 10-3 T 
B) 1.7 * 10-5 T 
C) 1.5 * 103 T 
D) 1.8 * 107 T 
E) 0.061 T

Question 17

A laser beam takes 100 ms to be reflected back from a totally reflecting sail on a spacecraft.How far away is the sail?

Accepted Answer

A) 1.5 * 107 m 
B) 3.0 * 107 m 
C) 4.5 * 107 m 
D) 6.0 * 107 m 
A) 1.5 * 107 m 
B) 3.0 * 107 m 
C) 4.5 * 107 m 
D) 6.0 * 107 m

Question 18

A parallel plate capacitor with circular plates of radius 10.0 cm are separated by a distance of 5.0 mm.The potential across the capacitor is increased at a constant rate of 120 V/s.Determine the magnitude of the magnetic field between the plates at a distance r = 1.0 cm from the center.

Accepted Answer

A) 1.3 * 10-15 T 
B) 3.6 * 10-15 T 
C) 4.9 * 10-15 T 
D) 6.6 * 10-15 T 
A) 1.3 * 10-15 T 
B) 3.6 * 10-15 T 
C) 4.9 * 10-15 T 
D) 6.6 * 10-15 T

Question 19

What is the frequency of a 100-cm radio wave?

Accepted Answer

A) 3 * 10-3 Hz 
B) 0.3 Hz 
C) 3 * 102 Hz 
D) 3 * 105 Hz 
E) 3 * 108 Hz 
A) 3 * 10-3 Hz 
B) 0.3 Hz 
C) 3 * 102 Hz 
D) 3 * 105 Hz 
E) 3 * 108 Hz

Question 20

A dipole antenna is located at the origin with its axis along the z-axis.As the antenna's electric current oscillates up and down the z-axis,polarized electromagnetic radiation travels away from the antenna along the positive y-axis.What is a possible direction of the radiation's oscillating magnetic field at point y=10m on the y-axis?

Accepted Answer

A) x-direction 
B) y-direction 
C) z-direction 
D) 45S1U1P1$\circ$S1S1P0 between the positive x- and positive y-directions 
E) 45S1U1P1$\circ$S1S1P0 between the positive x- and positive z-directions 
A) x-direction 
B) y-direction 
C) z-direction 
D) 45S1U1P1$\circ$S1S1P0 between the positive x- and positive y-directions 
E) 45S1U1P1$\circ$S1S1P0 between the positive x- and positive z-directions

Exam 31: Electromagnetic Waves

What is the time required for laser light to travel to the Moon and back? The radius of the Moon's orbit = 3.84 * 108 m.

Which waves have the shortest wavelength in the electromagnetic spectrum?

An electromagnetic wave with maximum electric field Emax = 44.0 V/m propagates in the x direction as shown.What is the intensity of this wave (in W/m2)?

A beam of unpolarized light goes through 3 polarizers.The axes of polarization for each make a 0 ∘\circ∘ ,20 ∘\circ∘ ,and 40 ∘\circ∘ angle with the vertical,respectively.What percent of the incident light makes it through?

What is the wavelength of the electromagnetic waves used for cell phone communications in the 850 MHz band?

Which waves have the smallest frequency in the electromagnetic spectrum?

The intensity of polarized light decreases to 2/3 of the incident intensity after passing through a polarizing filter.The angle between the electric field and the polarization axis of the filter is

A 10-mW vertically polarized laser beam passes through a polarizing filter whose axis is 30 degrees from the horizontal.What is the power in the laser beam that emerges from the polarizer?

The invisible heat rays of sunlight appear next to what color in the visible spectrum when sunlight is sent through a prism?

Which of the following exert the largest amount of radiation pressure?

An electric field has strength E = (65t - 22t2)V/m in a region of space.What is the displacement current through a circular area of diameter 15 cm in the x-y plane in this region at t = 5.0s?

The response of the human eye peaks at around 550 nm (green).The frequency corresponding to the green light is

How long does it take for light to travel from the Sun to Earth? (Hint: the distance between Earth and Sun is 148 million km.)

A laser beam takes 100 ms to be reflected back from a totally reflecting sail on a spacecraft.How far away is the sail?

A parallel plate capacitor with circular plates of radius 10.0 cm are separated by a distance of 5.0 mm.The potential across the capacitor is increased at a constant rate of 120 V/s.Determine the magnitude of the magnetic field between the plates at a distance r = 1.0 cm from the center.

What is the frequency of a 100-cm radio wave?

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Filters

What is the time required for laser light to travel to the Moon and back? The radius of the Moon's orbit = 3.84 * 10⁸ m.

An electromagnetic wave with maximum electric field Emax = 44.0 V/m propagates in the x direction as shown.What is the intensity of this wave (in W/m²)?

A beam of unpolarized light goes through 3 polarizers.The axes of polarization for each make a 0^$\circ$,20^$\circ$,and 40^$\circ$ angle with the vertical,respectively.What percent of the incident light makes it through?

An electric field has strength E = (65t - 22t²)V/m in a region of space.What is the displacement current through a circular area of diameter 15 cm in the x-y plane in this region at t = 5.0s?