Deck 25: Electromagnetic Waves

Question 1

For a beam of light,the direction of polarization is defined as

A)the beam's direction of travel.
B)the direction of the electric field's vibration.
C)the direction of the magnetic field's vibration.
D)the direction that is perpendicular to both the electric and magnetic field vectors.

Answer 1

the direction of the electric field's vibration.

Question 2

Which one of the following types of electromagnetic wave travels through space the fastest?

A)radio waves
B)infrared
C)ultraviolet
D)microwaves
E)They all travel through space at the same speed.

Answer 2

They all travel through space at the same speed.

Question 3

Which of the following statements about electromagnetic waves in free space are true? (There could be more than one correct choice. )

A)The higher-frequency travel faster than the lower-frequency waves.
B)The higher-frequency waves have shorter wavelengths than the lower-frequency waves.
C)The wavelengths of the visible waves are some of the longest electromagnetic waves.
D)The wavelengths of the visible waves are some of the shortest electromagnetic waves.
E)The electric field vector is always at right angles to the magnetic field vector.

Answer 3

The higher-frequency waves have shorter wavelengths than the lower-frequency waves.
The electric field vector is always at right angles to the magnetic field vector.

Question 4

A certain part of the electromagnetic spectrum ranges from 200 nm to 400 nm.What is the lowest frequency associated with this portion of the spectrum? (c = 3.00 × 10⁸ m/s)

A)1.50 × 10¹⁴ Hz
B)7.50 × 10¹³ Hz
C)7.50 × 10¹⁴ Hz
D)7.50 × 10¹⁵ Hz
E)1.50 × 10¹⁵ Hz

Question 5

Which one of the following lists gives the correct order of the electromagnetic spectrum from low to high frequencies?

A)radio waves,infrared,microwaves,ultraviolet,visible,x-rays,gamma rays
B)radio waves,ultraviolet,x-rays,microwaves,infrared,visible,gamma rays
C)radio waves,microwaves,infrared,visible,ultraviolet,x-rays,gamma rays
D)radio waves,microwaves,visible,x-rays,infrared,ultraviolet,gamma rays
E)radio waves,infrared,x-rays,microwaves,ultraviolet,visible,gamma rays

Question 6

Which one of the following is not an electromagnetic wave?

A)ultraviolet
B)infrared
C)radio waves
D)sound waves
E)gamma rays

Question 7

The frequency of a microwave signal is 9.76 GHz.What is its wavelength? (c = 3.00 × 10⁸ m/s)

A)3.07 cm
B)2.07 cm
C)1.07 cm
D)5.07 cm
E)4.07 cm

Question 8

The wavelength of an electromagnetic wave is 600 nm.What is its frequency? (c = 3.0 × 10⁸ m/s)

A)200 × 10¹² Hz
B)300 × 10¹² Hz
C)400 × 10¹² Hz
D)500 × 10¹² Hz
E)600 × 10¹² Hz

Question 9

Which one of the following expressions is the correct representation for the speed of light in vacuum?

A)
B)
C)
D)1 /
E)1 / ε₀μ₀

Question 10

What is the wavelength used by a radio station that broadcasts at a frequency of 920 kHz? (c = 3.00 × 10⁸ m/s)

A)22.6 m
B)226 m
C)326 m
D)175 m
E)276 m

Question 11

For a certain electromagnetic wave in free space,at one instant the electric field vector points in the +z direction while the magnetic field vector points in the +x direction,as shown in the figure.In what direction is this wave traveling?

A)+x
B)-x
C)+y
D)-y
E)+z

Question 12

For an electromagnetic wave in free space having an electric field of amplitude E and a magnetic field of amplitude B,the ratio of B/E is equal to

A)c.
B)c².
C)1/c.
D)1/c².
E) .

Question 13

In an electromagnetic wave in free space,the electric and magnetic fields are

A)parallel to one another and perpendicular to the direction of wave propagation.
B)parallel to one another and parallel to the direction of wave propagation.
C)perpendicular to one another and perpendicular to the direction of wave propagation.
D)perpendicular to one another and parallel to the direction of wave propagation.

Question 14

At a certain instant in time,the electric field of an electromagnetic wave in free space points in the -z direction,and the magnetic field points in the +y direction.In what direction is this wave traveling?

A)+x direction
B)-x direction
C)+y direction
D)-z direction
E)+z direction

Question 15

An electromagnetic wave is propagating towards the west in free space.At a certain moment the direction of the magnetic field vector associated with this wave points vertically upward.What is the direction of the electric field vector?

A)horizontal and pointing south
B)vertical and pointing down
C)horizontal and pointing north
D)vertical and pointing upward
E)horizontal and pointing east

Question 16

A certain part of the electromagnetic spectrum ranges from 200 nm to 400 nm.What is the highest frequency associated with this portion of the spectrum? (c = 3.00 × 10⁸ m/s)

A)1.50 × 10¹⁴ Hz
B)7.50 × 10¹³ Hz
C)7.50 × 10¹⁴ Hz
D)7.50 × 10¹⁵ Hz
E)1.50 × 10¹⁵ Hz

Question 17

An electromagnetic wave travels in free space in the +y direction,as shown in the figure.If the electric field at the origin is along the +z direction,what is the direction of the magnetic field?

A)+z
B)-z
C)+y
D)+x
E)-x

Question 18

What is the frequency of 20-mm microwaves? (c = 3.0 × 10⁸ m/s)

A)100 MHz
B)400 MHz
C)15 GHz
D)73 GHz

Question 19

Which one of the following lists gives the correct order of the electromagnetic waves from longer wavelength to shorter wavelength?

A)radio waves,infrared,microwaves,ultraviolet,visible,x-rays,gamma rays
B)radio waves,ultraviolet,x-rays,microwaves,infrared,visible,gamma rays
C)radio waves,microwaves,visible,x-rays,infrared,ultraviolet,gamma rays
D)radio waves,microwaves,infrared,visible,ultraviolet,x-rays,gamma rays
E)radio waves,infrared,x-rays,microwaves,ultraviolet,visible,gamma rays

Question 20

If unpolarized light of intensity I₀ passes through an ideal polarizer,what is the intensity of the emerging light?

A)I₀
B)I₀/2
C)I₀/4
D)I₀/
E)I₀/16

Question 21

A laser beam takes 24 ms to travel from a rocket to the reflective surface of a planet and back to the rocket.How far is the rocket from this planet's surface? (c = 3.0 × 10⁸ m/s)

A)2400 km
B)1200 km
C)1800 km
D)3600 km
E)4800 km

Question 22

A radar receiver indicates that a pulse return as an echo in 20 μs after it was sent.How far away is the reflecting object? (c = 3.0 × 10⁸ m/s)

A)1.5 km
B)3.0 km
C)6.0 km
D)9.0 km

Question 23

A radiometer has two square vanes (1.0 cm by 1.0 cm),attached to a light horizontal cross arm,and pivoted about a vertical axis through the center,as shown in the figure.The center of each vane is 6.0 cm from the axis.One vane is silvered and it reflects all radiant energy that falls upon it.The other vane is blackened and it absorbs all incident radiant energy.Radiant energy,having an intensity of 300 W/m²,is incident normally upon the front surfaces of both vanes.What is the radiant power absorbed by the blackened vane?

A)0.030 W
B)0.040 W
C)0.050 W
D)0.060 W
E)0.090 W

Question 24

A 7.55 ×
Hz electromagnetic wave travels in carbon tetrachloride with a speed of 2.05 × 10⁸ m/s.What is the wavelength of the wave in this material?

A)272 nm
B)301 nm
C)338 nm
D)361 nm
E)397 nm

Question 25

About 1350 W/m² of electromagnetic energy reaches the upper atmosphere of the earth from the sun,which is 1.5 × 10¹¹ m away.Use this information to estimate the average power output of the sun.

A)1 × 10²⁶ W
B)2 × 10²⁶ W
C)3 × 10²⁶ W
D)4 × 10²⁶ W

Question 26

How far does a beam of light travel through space in one 365-day year? (c = 3.0 × 10⁸ m/s)

A)80 × 10¹² m
B)95 × 10¹⁴ m
C)30 × 10⁸ m
D)20 × 10¹⁵ m
E)36 × 10¹⁶ m

Question 27

A certain electromagnetic field traveling in vacuum has a maximum electric field of 1200 V/m.What is the maximum magnetic field of this wave? (c = 3.0 × 10⁸ m/s)

A)3.4 × 10^-4 T
B)4.0 × 10^-6 T
C)2.2 × 10^-5 T
D)9.6 × 10^-6 T
E)8.7 × 10^-6 T

Question 28

The distance between two asteroids is 1600 km.How much time does it take for a light signal to go from one asteroid to the other? (c = 3.0 × 10⁸ m/s)

A)19 ms
B)4.5 ms
C)5.3 ms
D)13 ms
E)19 µs

Question 29

A radio station broadcasts at 80 MHz.How long does it take for this radio signal to travel a distance of
Through space? (c = 3.0 × 10⁸ m/s)

A)0.15 × 10^-2 s
B)15 ms
C)6.7 × 10^-2 s
D)20 ms
E)25 ms

Question 30

If the magnetic field in a traveling electromagnetic wave has a maximum value of 16.5 nT,what is the maximum value of the electric field associated with this wave? (c = 3.00 × 10⁸ m/s)

A)5.5 × 10^-17 V/m
B)4.95 V/m
C)0.495 V/m
D)55.0 × 10^-16 V/m
E)55.0 × 10^-15 V/m

Question 31

How far does light travel in 1.0 μs? (c = 3.0 × 10⁸ m/s)

A)3.0 × 10¹⁴ m
B)0.30 km
C)3.0 m
D)30 cm

Question 32

A radio station broadcasts at a frequency of 80 MHz.How far from the transmitter will this signal travel in 67 ms? (c = 3.0 × 10⁸ m/s)

A)60 × 10⁶ m
B)67 m
C)40 km
D)80 km
E)20 × 10⁶ m

Question 33

Radiation of a single frequency reaches the upper atmosphere of the earth with an intensity of 1350 W/m².What is the maximum value of the electric field associated with this radiation? (c = 3.00 × 10⁸ m/s,μ₀ = 4π × 10^-7 T ∙ m/A,ε₀ = 8.85 × 10^-12 C²/N ∙ m²)

A)675.0 V/m
B)1604 V/m
C)1400 V/m
D)1350 V/m
E)1010 V/m

Question 34

The maximum value of the electric field in an electromagnetic wave is 2.0 V/m.What is the maximum value of the magnetic field in that wave? (c = 3.0 × 10⁸ m/s)

A)6.7 pT
B)6.7 mT
C)6.7 nT
D)6.7 μT
E)6.7 T

Question 35

The amplitude of the electric field for a certain type of electromagnetic wave is 570 N/C.What is the amplitude of the magnetic field for that wave? (c = 3.00 × 10⁸ m/s)

A)2.91 µT
B)1.90 µT
C)1.10 µT
D)1.41 µT
E)2.41 µT

Question 36

A sinusoidal electromagnetic wave has a peak electric field of
What is the intensity of the wave?

A)170 kW/m²
B)85 kW/m²
C)21 kW/m²
D)11 kW/m²

Question 37

A radio transmitter is operating at an average power of
And is radiating uniformly in all directions.What is the average intensity of the signal
From the transmitter?

A)4.97 μW/m²
B)2.49 μW/m²
C)0.00497 W/m²
D)0.00249 W/m²

Question 38

How far does a beam of light travel in 2.0 ms? (c = 3.0 × 10⁸ m/s)

A)6.0 × 10⁵ m
B)0.66 × 10⁵ m
C)90 m
D)70 m
E)60 m

Question 39

How long does it take light to travel 1.0 m? (c = 3.0 × 10⁸ m/s)

A)3.3 ns
B)3.3 μs
C)3.3 ms
D)3.3 s

Question 40

How much time does it take a beam of light to travel 2.9 km through space? (c = 3.0 × 10⁸ m/s)

A)9.7 s
B)9.7 ms
C)9.7 μs
D)9.7 ns
E)9.7 ps

Question 41

Unpolarized light is incident upon two ideal polarizing filters that do not have their transmission axes aligned.If 19% Of the light passes through this combination,what is the angle between the transmission axes of the two filters?

A)52°
B)72°
C)0°
D)0°..

Question 42

What is the maximum value of the magnetic field at a distance of 2.5 m from a light bulb that radiates 100 W of single-frequency sinusoidal electromagnetic waves uniformly in all directions? (ε₀ = 8.85 × 10^-12 C²/N ∙ m²,μ₀ = 4π × 10^-7 T ∙ m/A,c = 3.0 × 10⁸ m/s)

A)0.10 μT
B)0.40 μT
C)0.50 μT
D)0.60 μT
E)0.80 μT

Question 43

The following items are positioned in sequence: A source of a beam of natural light of intensity I₀,three ideal polarizers A,B,and C;and an observer.Polarizer axis angles are measured clockwise from the vertical,as viewed by the observer.The axis angle of polarizer A is set at 0° (vertical),and the axis angle of polarizer C is set at 50°.The axis angle of polarizer B is set at 120°.What is ratio of the intensity of the beam at the observer to the intensity I₀ of the source?

A)0.015
B)0.020
C)0.025
D)0.030
E)0.035

Question 44

An 800-kHz sinusoidal radio signal is detected at a point 2.1 km distant from a transmitter tower.The electric field amplitude of the signal at that point is 0.80 V/m.Assume that the signal power is radiated uniformly in all directions and that radio waves incident upon the ground are completely absorbed.What is the intensity of the radio signal at that point? (ε₀ = 8.85 × 10^-12 C²/N ∙ m²,μ₀ = 4π × 10^-7 T ∙ m/A,c = 3.0 × 10⁸ m/s)

A)8.5 × 10^-4 W/m²
B)1.2 × 10^-3 W/m²
C)1.7 × 10^-3 W/m²
D)6.0 × 10^-4 W/m²
E)4.2 × 10^-4 W/m²

Question 45

The following items are positioned in sequence: A source of a beam of natural light of intensity I₀,three ideal polarizers A,B,and C;and an observer.Polarizer axis angles are measured clockwise from the vertical,as viewed by the observer.The axis angle of polarizer A is set at 0° (vertical),and the axis angle of polarizer C is set at 50°.Polarizer B is set so that the beam intensity is zero at the observer.What are the two possible axis angle settings (less than 180°)of polarizer B?

A)40° and 90°
B)40° and 130°
C)40° and 140°
D)90° and 130°
E)90° and 140°

Question 46

A beam of light is polarized in a vertical plane and has an intensity I₀.The beam passes through an ideal polarizer and then through an ideal analyzer whose axis is set horizontally.If the axis of the polarizer is set at 60° with the vertical,what is the ratio of the intensity of the final beam to I₀?

A)0.19
B)0.25
C)0.31
D)0.37
E)0.43

Question 47

An ideal polarizer with its transmission axis rotated 30° to the vertical is placed in a beam of unpolarized light of intensity 10 W/m².After passing through the polarizer,what is intensity of the beam?

A)2.5 W/m²
B)5.0 W/m²
C)8.7 W/m²
D)7.5 W/m²
E)10 W/m²

Question 48

Light of intensity S₀ that is polarized horizontally passes through three ideal polarizers.The first and third are horizontal,but the second one is oriented at
To the horizontal.In terms of S₀,the intensity of the light that passes through the set of polarizers is closest to which one of the following choices?

A)0.729 S₀
B)0.125 S₀
C)0.427 S₀
D)0.854 S₀

Question 49

Polarized light of intensity S₀ passes through an ideal polarizer.If the electric vector of the polarized light is horizontal what,in terms of the initial intensity S₀,is the intensity of the light that passes through a polarizer if that polarizer is tilted
From the horizontal?

A)0.812 S₀
B)0.188 S₀
C)0.217 S₀
D)0.284 S₀

Question 50

As shown in the figure,the orientation of the transmission axis for each of three ideal polarizing sheets is labeled relative to the vertical direction.A beam of light,polarized in the vertical direction,is incident on the first polarizer with an intensity of 1.00 kW/m².What is the intensity of the beam after it has passed through the three polarizing sheets when θ₁ = 30°,θ₂ = 30°,and θ₃= 60°?

A)141 W/m²
B)316 W/m²
C)433 W/m²
D)563 W/m²
E)188 W/m²

Question 51

A light source radiates 60.0 W of single-wavelength sinusoidal light uniformly in all directions.What is the amplitude of the magnetic field of this light at a distance of 0.700 m from the bulb? (ε₀ = 8.85 × 10^-12 C²/N ∙ m²,μ₀ = 4π × 10^-7 T ∙ m/A,c = 3.0 × 10⁸ m/s)

A)1.76 × 10^-7 T
B)2.02 × 10^-7 T
C)2.22 × 10^-7 T
D)2.86 × 10^-7 T

Question 52

An 8.00-mW laser beam emits a cylindrical beam of single-wavelength sinusoidal light 0.600 mm in diameter.What is the maximum value of the magnetic field in the laser beam? (ε₀ = 8.85 × 10^-12 C²/N ∙ m²,μ₀ = 4π × 10^-7 T ∙ m/A,c = 3.0 × 10⁸ m/s)

A)9.24 µT
B)17.2 µT
C)12.4 µT
D)20.5 µT
E)15.4 µT

Question 53

The following items are positioned in sequence: A source of a beam of natural light of intensity I₀,three ideal polarizers A,B,and C;and an observer.Polarizer axis angles are measured clockwise from the vertical,as viewed by the observer.The axis angle of polarizer A is set at 0° (vertical),and the axis angle of polarizer C is set at 50°.Polarizer B is set so that the beam intensity at the observer is a maximum.What is the axis angle settings of polarizer B?

A)0°
B)25°
C)50°
D)75°
E)100°

Question 54

A light source radiates 60.0 W of single-wavelength sinusoidal light uniformly in all directions.What is the amplitude of the electric field of this light at a distance of 0.400 m from the bulb? (ε₀ = 8.85 × 10^-12 C²/N ∙ m²,μ₀ = 4π × 10^-7 T ∙ m/A,c = 3.00 × 10⁸ m/s)

A)162 N/C
B)212 N/C
C)82.1 N/C
D)150 N/C
E)52.9 N/C

Question 55

How much energy is transported across a 1.00-cm² area per hour by a sinusoidal electromagnetic wave whose electric field has a maximum strength of 30.4 V/m? (ε₀ = 8.85 × 10^-12 C²/N ∙ m²,μ₀ = 4π × 10^-7 T ∙ m/A,c = 3.0 × 10⁸ m/s)

A)0.44 nJ
B)0.44 μJ
C)0.44 mJ
D)0.44 J

Question 56

A light source radiates 60.0 W of single-wavelength sinusoidal light uniformly in all directions.What is the average intensity of the light from this bulb at a distance of 0.400 m from the bulb?

A)14.9 W/m²
B)37.2 W/m²
C)27.4 W/m²
D)11.9 W/m²
E)29.8 W/m²

Question 57

The rate of energy flow per unit area of an electromagnetic wave has an average value of 0.695 W/m².The wave is incident at right angles upon a rectangular area measuring 1.5 m by 2.0 m.How much total energy falls upon this rectangle each minute? (ε₀ = 8.85 × 10^-12 C²/N ∙ m²,μ₀ = 4π × 10^-7 T ∙ m/A,c = 3.0 × 10⁸ m/s)

A)130 J
B)160 J
C)190 J
D)220 J
E)250 J

Question 58

An 800-kHz sinusoidal radio signal is detected at a point 6.6 km from the transmitter tower.The electric field amplitude of the signal at that point is 0.780 V/m.Assume that the signal power is radiated uniformly in all directions and that radio waves incident upon the ground are completely absorbed.What is the amplitude of the magnetic field of the signal at that point? (ε₀ = 8.85 × 10^-12 C²/N ∙ m²,c = 3.0 × 10⁸ m/s,μ₀ = 4π × 10^-7 T ∙ m/A)

A)2.6 nT
B)2.1 nT
C)1.6 nT
D)3.1 nT
E)3.6 nT

Question 59

The rate of energy flow per unit area of a sinusoidal electromagnetic wave has an average value of 0.601 W/m².What is the maximum value of the magnetic field in the wave? (c = 3.00 × 10⁸ m/s,μ₀ = 4π × 10^-7 T ∙ m/A,ε₀ = 8.85 × 10^-12 C²/N ∙ m²)

A)7.09 × 10^-8 _T
B)5.02 × 10^-8 _T
C)3.55 × 10^-8 _T
D)9.81 × 10^-8 _T
E)1.42 × 10^-7 _T

Question 60

An 8.0-mW laser beam emits a cylindrical beam of single-wavelength sinusoidal light 0.90 mm in diameter.What is the rms value of the electric field in this laser beam? (ε₀ = 8.85 × 10^-12 C²/N ∙ m²,μ₀ = 4π × 10^-7 T ∙ m/A,c = 3.0 × 10⁸ m/s)

A)2200 N/C
B)1000 N/C
C)1100 N/C
D)4100 N/C
E)2000 N/C

Question 61

Unpolarized light passes through a combination of two ideal polarizers.The transmission axes of the first polarizer and the second polarizer are at 30.0° to each other.What percentage of the original light gets through the combination?

A)37.5%
B)50%
C)75%
D)100%

Question 62

Unpolarized light passes through three ideal polarizing filters.The first filter is oriented with a horizontal transmission axis,the second one has its transmission axis at 30° from the horizontal,and the third filter has a vertical transmission axis.What percent of the light gets through this combination?

A)9.4%
B)91%
C)50%
D)0%
E)33%

Question 63

A vertically polarized beam of light of intensity 100 W/m² passes through two ideal polarizers.The transmission axis of the first polarizer makes an angle of 20.0° with the vertical,and the transmission axis of the second one makes an angle of 40.0° with the vertical.What is the intensity of the light after it has passes through both polarizers?

A)22.2 W/m²
B)44.4 W/m²
C)66.6 W/m²
D)78.0 W/m²
E)11.7 W/m²