Deck 31: Electromagnetic Waves

Question 1

The potential across a 10 mF capacitor is increasing at a constant rate.If the displacement current through the capacitor is 10.0 A,what is the rate at which the potential difference is increasing across the capacitor's plates.

A)100 V/s
B)120 V/s
C)50 V/s
D)None are correct.

Answer 1

None are correct.

Question 2

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 20-W 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,what is her acceleration towards the shuttle?

A)1.3 * 10^-9 m/s²
B)1.6 * 10^-9 m/s²
C)1.9 * 10^-9 m/s²
D)2.1 * 10^-9 m/s²
E)2.3 * 10^-9 m/s²

Answer 2

1.3 * 10^-9 m/s²

Question 3

Which waves have the smallest frequency in the electromagnetic spectrum?

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

Answer 3

radio waves

Question 4

Which four quantities do Maxwell's Equations relate to each other?

A)electric field,capacitance,resistance,and inductance
B)electric field,charge,current,and voltage
C)electric field,magnetic field,charge,and current
D)electric field,magnetic field,energy,and power

Question 5

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 20 W 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.What is her total mass with equipment if her resulting acceleration is 1.6 * 10^-9 m/s² towards the shuttle?

A)84 kg
B)119 kg
C)100 kg
D)110 kg
E)133 kg

Question 6

At a certain instant in time,in an electromagnetic wave,the electric field vector points to the north and the magnetic field vector points vertically downward.In which direction is the electromagnetic wave moving?

A)east
B)north
C)west
D)south

Question 7

Which waves have the highest frequency in the electromagnetic spectrum?

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

Question 8

The potential across a capacitor is increasing at a rate of 120 V/s.If the displacement current through the capacitor is 10.0 A,what is the capacitance of the capacitor?

A)10.0 mF
B)100 mF
C)83 mF
D)None are correct.

Question 9

What creates magnetic fields?

A)moving charges
B)changing electric fields
C)Both A and B are correct.
D)None are correct.

Question 10

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.

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 11

An electric field of 100 V/m is directed outward from the plane of a circular area with radius 4.0 cm.If the electric field increases at a rate of 10 V/ms,determine the magnitude of the magnetic field at a radial distance 10.0 cm away from the center of the circular area.

A)1.1 * 10^-15 T
B)3.4 * 10^-15 T
C)5.9 * 10^-15 T
D)8.9 * 10^-15 T
E)9.7 * 10^-15 T

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?

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

Question 13

Which waves have the shortest wavelength in the electromagnetic spectrum?

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

Question 14

Which waves have the longest wavelength in the electromagnetic spectrum?

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

Question 15

A laser beam is reflected back from a totally reflecting sail on a spacecraft that is 4.5 * 10⁷ m from the source of the beam.How long after the beam is sent does it return to the source?

A)100 ms
B)200 ms
C)150 ms
D)300 ms

Question 16

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.If the magnitude of the magnetic field between the plates at a distance r = 1.0 cm from the center is 3.6 * 10^-15 T,what is the rate of increase in the potential across the plates of the capacitor?

A)320 V/s
B)120 V/s
C)220 V/s
D)420 V/s

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?

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.Find the distance from the center of the plates and between the plates (r<10cm)where the magnetic field is 3.6 * 10^-15 T.

A)5.0 cm
B)1.4 cm
C)2.7 cm
D)7.1 cm

Question 19

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.Find the distance from the center of the plates,outside of the space between the plates (r >10cm)where the magnetic field is 3.6 * 10^-15 T.

A)46 cm
B)27 cm
C)54 cm
D)37 cm

Question 20

The potential across a 10.0-mF capacitor is increasing at a rate of 120 V/s.What is the displacement current through the capacitor?

A)1.20 A
B)10.0 A
C)120 A
D)None are correct.

Question 21

What is the distance between successive heating anti-nodes in a microwave oven's cavity? The microwave oven uses 1200 W and uses a frequency of 2.4 Gigahertz.

A)0.30 mm
B)0.60 mm
C)6.3 cm
D)13 cm
E)26 cm

Question 22

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?

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

Question 23

An industrial CO₂ laser produces a beam of radiation with average power of 5.60 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 148 $\mu$ m.The laser light is completely absorbed by small spherical dust particle with diameter of 50 $\mu$ m.What is the force that the laser beam exerts on the dust particle (before it is incinerated!)?

A)3.2 * 10^-6 N
B)4.2 * 10^-6 N
C)8.6 * 10^-6 N
D)1.9 * 10^-5 N
E)2.1 * 10^-6 N

Question 24

Unpolarized light of intensity 100 mW/m² passes through two filters.The first filter has an alignment of 30.0 degrees from the vertical and the second has an alignment of 80.0 degrees from the vertical.What is the intensity of the light that passes through the second filter?

A)1.1 mW/m²
B)2.3 mW/m²
C)21 mW/m²
D)24 mW/m²
E)41 mW/m²

Question 25

A laser having with a spot 1.00 mm in diameter is shone perpendicularly on the center of a thin,perfectly reflecting circular (2.00 mm in diameter)aluminum plate mounted vertically on a flat piece of cork that floats on the surface of the water in a large beaker.The mass of this "sailboat" is 0.0550 g and it travels 3.00 mm in 50.0 s.Assuming that the laser power is constant in the region where the sailboat is located during the experiment,what is the power of the laser used in this demonstration? (Neglect air resistance and the viscosity of the water.)

A)34.6 mW
B)25.2 mW
C)22.7 mW
D)19.8 mW
E)15.1 mW

Question 26

Unpolarized light of intensity 100 mW/m² passes through two filters.The first filter has an alignment of 30.0 degrees from the vertical.The intensity of the light that passes through the second filter is 41 mW/m². What is the angular alignment of the second filter with respect to the vertical?

A)5 degrees
B)10 degrees
C)15 degrees
D)20 degrees
E)25 degrees

Question 27

A cell phone transmits 2.0 W of power at 380 MHz in a spherical pattern.What is the intensity of the radiation at the cell tower,located 3.0 km away?

A)1.8 * 10^-11 W/m²
B)1.8 * 10^-8 W/m²
C)2.2 * 10^-7 W/m²
D)6.7 * 10^-4 W/m²
E)6.84 W/m²

Question 28

Sunlight is coming straight down on a solar panel (length 1.25 m and width W=0.850 m)belonging to the Spirit Mars rover.The amplitude of the electric field in the solar radiation is 642 V/m and is uniform (the radiation has the same amplitude everywhere).Find the efficiency of the solar panel if average electrical power converted from the solar radiation is 131 W.

A)20.4 %
B)26.0 %
C)18.9 %
D)22.6%
E)24.5 %

Question 29

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.

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 30

A monochromatic point like light source emits electromagnetic power uniformly in all directions.The Poynting vector in a point situated at 0.500 m from the source is 0.375 W/m².The power of the source is

A)1.00 W.
B)1.18 W.
C)1.29 W.
D)1.32 W.
E)1.45 W.

Question 31

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

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

Question 32

A laser produces linearly polarized light that is polarized in the vertical direction.The light travels in the +y-direction and passes through two polarizers.The polarization axis of the first polarizer is tipped towards the negative x-axis at 24 ^$\circ$ from vertical (z-axis).The polarization axis of the second polarizer is tipped towards the positive x-axis at 15 ^$\circ$ from vertical (z-axis).The laser beam is collimated (neither converging nor expanding),has a circular cross section with a diameter of 1.00 mm,and has an average power of 15 mW.What is the average power of the laser beam after passing through both polarizers?

A)3.75 W
B)7.56 W
C)10.6 W
D)11.7 W
E)12.5 W

Question 33

A monochromatic point like light source emits 1.50 W of electromagnetic power uniformly in all directions.How far from the point source is the Poynting vector 0.367 W/m²?

A)0.65 m
B)0.75 m
C)0.51 m
D)0.57 m
E)0.88 m

Question 34

There are two polarizing filters that are out of alignment by 30 degrees.If light of intensity 1.00 W/m² and initially polarized half-way between the two filters passes through the two filters,what is the intensity of the transmitted light?

A)0.375 W/m²
B)0.563 W/m²
C)0.700 W/m²
D)0.750 W/m²
E)0.837 W/m²

Question 35

A monochromatic point like light source emits 1.50 W of electromagnetic power uniformly in all directions.The Poynting vector in a point situated at 0.750 m from the source is

A)0.212 W/m².
B)0.119 W/m².
C)0.367 W/m².
D)0.0578 W/m².
E)0.437 W/m².

Question 36

Sunlight is coming straight down on a solar panel (length 1.25 m and width W=0.850 m)belonging to the Spirit Mars rover.The amplitude of the electric field in the solar radiation is 642 V/m and is uniform (the radiation has the same amplitude everywhere).If the solar panel has an efficiency of 20.4 percent in converting solar radiation into electrical power,how much average power can the panel generate from the solar radiation?

A)100 W
B)119 W
C)131 W
D)237 W
E)581 W

Question 37

A cell phone transmits 2.0 W of power at 380 MHz in a spherical pattern.What is the rms value of the electric field on the electron in the receiving antenna,located 3.0 km away?

A)1.5 * 10^-7 V/m
B)6.8 * 10^-6 V/m
C)1.3 * 10^-4 V/m
D)2.6 * 10^-3 V/m
E)2.3 V/m

Question 38

A plane parallel plate capacitor has air between plates and disc shaped plates of radius 3.0 mm that are coaxial and 2.5 mm apart.Charge is being accumulated on the plates of the capacitor.What is the displacement current between the plates at an instant when the time rate of charge accumulation on the plates is 1.5 $\mu$ C/s?

A)1.0 * 10^-6 A
B)1.5 * 10^-6 A
C)2.0 * 10^-6 A
D)2.5 * 10^-6 A
E)3.0 * 10^-6 A

Question 39

Which of the following exert the largest amount of radiation 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 40

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 20-W 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,how long will it take her to reach the space shuttle?

A)2.2 hours
B)10 hours
C)23 hours
D)48 hours

Question 41

A small,perfectly reflecting Mylar disc,density 1.1 g/cm³,radius 0.15 mm,thickness 0.050 mm,is levitated by a laser,whose beam at the point of interaction of beam and disc is 0.35 mm in diameter.Assuming the disc is levitating in a horizontal orientation,what power does the laser emit?

A)5.7 W
B)7.8 W
C)11 W
D)16 W
E)31 W

Question 42

A parallel plate capacitor with radius 21 cm is connected in series with a 15-V battery.A switch is thrown which causes the capacitor to discharge through a 150- $\varOmega$ resistor.What is the displacement current between the plates at this time?

A)0.10 A
B)0.20 mA
C)0.14 A
D)You need to know the separation of the plates.

Question 43

Which of the following exert the smallest amount of radiation 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 44

Multiwall Carbon Nanotubes (MWCN)can be synthesized by heating an SiC wafer by a high power laser such as a CO₂ laser.If the diameter of a laser beam of 3-kW power and 10-µm wavelength is 3 mm,what force does the laser beam exert on the SiC wafer?

A)9.8 * 10^-4 N
B)3.12 * 10^-5 N
C)1.00 * 10^-5 N.
D)7.50 * 10^-6 N

Question 45

The amplitude of the electric field detected by an FM radio receiver is 400 µV/m.The intensity of the signal is

A)1.2 * 10^-10 W/m².
B)2.1 * 10^-10 W/m².
C)2.4 * 10^-10 W/m².
D)9.8 * 10^-10 W/m².

Question 46

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?

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

Question 47

The current flowing in a 20-cm long and 2-cm radius solenoid having 500 turns decreases from 3 A to 1 A in 0.1 seconds.Determine the magnitude of the induced electric field inside the solenoid 1-cm from its center.

A)5 * 10^-1 V/m
B)5 * 10^{-4 V/m}
C)3 * 10^{-4 V/m}
D)3 * 10^{-2 V/m}

Question 48

What is the electric field amplitude of an electromagnetic wave whose magnetic field amplitude is 5 * 10^-3 T?

A)6.7 * 10⁵ V/m
B)1.5 * 10⁶ V/m
C)6.7 * 10⁶ V/m
D)1.5 * 10³ V/m

Question 49

The amplitude of the electric field of an electromagnetic wave is 21 V/m.The amplitude of the magnetic field of the wave is

A)63 * 10^-8 T.
B)49 * 10^-8 T.
C)31* 10^-8 T.
D)7 * 10^-8 T.

Question 50

What is the direction of the net force on the moving charge in figure shown?

A)into the page
B)right
C)out of the page
D)left

Question 51

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

A)2.5 mW
B)7.5 mW
C)5.6 mW
D)1.9 mW

Question 52

The unit of the quantity $\varepsilon$ ₀(d $\varPhi$ _E/dt)is

A)amperes.
B)volts.
C)ampere.meters.
D)volt.meters.

Question 53

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?

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

Question 54

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?

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

Question 55

The power of a light bulb is 100 W on a circular disk of radius 2 mm at a distance of 1m.What is the power on a 4-mm disk at a distance of 2 m from the same bulb?

A)25 W
B)50 W
C)100 W
D)200 W
E)400 W

Question 56

A house with a south-facing roof installs photovoltaic panels on its roof to generate electricity.The photovoltaic panels have an efficiency of 10% and occupy an area with a size of 5.0 m by 8.0 m.The average solar radiation on the panels is 250 W/m²,when averaged over day/night,summer/winter,cloudy/sunny,etc.How many kilowatt-hours of electrical energy will the solar panels generate in a 30-day month?

A)720 kW-hr
B)1000 kW-hr
C)1200 kW-hr
D)1500 kW-hr
E)10000 kW-hr

Question 57

Unpolarized light of intensity 200 W/m² is incident on a polarizer A. Light leaving this polarizer is then incident on a polarizer B with its polarization axis oriented at 30 ^$\circ$ with respect to that of A. What is the intensity of the light leaving polarizer B?

A) 25 W/m²
B) 75 W/m²
C) 100 W/m²
D) 150 W/m²
E) 200 W/m²

Question 58

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)54.7 ^$\circ$ .
B)35.3 ^$\circ$ .
C)29.1 ^$\circ$ .
D)25.0 ^$\circ$ .

Question 59

A parallel plate capacitor with radius 21 cm is connected in series 15-V battery.A switch is thrown which causes the capacitor to discharge through a 150- $\varOmega$ resistor.What is the magnetic field 1.0 cm from the axis defined by the centers of the plates at this time?

A)1.0 * 10^-12 T
B)3.1 * 10^-12 T
C)2.1 * 10^-11 T
D)4.5 * 10^-9 T
E)You need to know the separation of the plates.

Question 60

A focused 100 W spotlight delivers 50% of its light into a circle with a diameter of 50 cm.What is the average rms electric field in this illuminated area?

A)150 V/m
B)190 V/m
C)250 V/m
D)310 V/m
E)440 V/m

Question 61

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

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

Question 62

Unpolarized light with intensity I₀ is incident on a polarizer as shown.After passing through the first polarizer,the light has intensity I₁.This light passes through a second polarizer that is rotated 45 ^$\circ$ with respect to the first polarizer.The light now with intensity I₂ passes through a third polarizer that is rotated 90 ^$\circ$ with respect to the first polarizer.The intensity of light after the third polarizer is I₃.Pick the one correct statement from the following statements.

A)I₃ = 0
B)I₃ = I₀/8
C)I₃ = I₀/3
D)I₃ = 2I₀
E)I₃ = I₀/2

Question 63

Which waves travel fastest in vacuum?

A)red light
B)blue light
C)x-rays
D)gamma-rays
E)They all travel with the same speed.

Question 64

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?

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

Question 65

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

Question 66

Laser light with an intensity of 40,000 W/m² perpendicularly hits a black perfect absorber rectangular area of width W = 27 mm and height H = 35 mm.What is the force this laser exerts on the area?

A)1.26 * 10^-7 N
B)33.8 N
C)2.2 N
D)34.5 * 10^-6 N
E)9.8 * 10^-15 N

Question 67

A green laser beam with a wavelength of 515 nm is transmitting a signal to a satellite.If it takes 1.0 ms for the signal to reach the satellite,how far away is the satellite?

A)300 km
B)515 km
C)1900 km
D)3300 km
E)300,000 km

Question 68

A 5-mW laser pointer has a beam diameter of 3 mm.What is the total electromagnetic energy in a 2.0 m length of this laser beam?

A)2.3 * 10^-16 J
B)4.7 * 10^-16 J
C)1.7 * 10^-11 J
D)3.3 * 10^-11 J
E)5.0 * 10^-3 J

Question 69

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

Question 70

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.

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

Question 71

Point out the incorrect statement with respect to an electromagnetic wave in vacuum (or air).

A)The color depends on the wavelength.
B)The energy is transported with speed c in the direction of propagation.
C)Both the electric field and the magnetic field exist in a plane perpendicular to the direction of propagation.
D)The electric and the magnetic fields change in time,but do not change with position in space.
E)The electric field vector and the magnetic field vector are always perpendicular to each other.

Question 72

A beam of unpolarized light with an intensity of 1000 W/m² impinges on a set of two linear polarizers with their polarization axes at an angle $\theta$ relative to each other.If the light transmitted through this combination has an intensity of 250 W/m²,what is $\theta$ ?

A)0 ^$\circ$
B)22.5 ^$\circ$
C)45 ^$\circ$
D)67.5 ^$\circ$
E)90 ^$\circ$

Question 73

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

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

Question 74

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

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