Question 1

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)

Accepted Answer

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

Question 2

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

Accepted Answer

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 
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 3

A sinusoidal electromagnetic wave is propagating in vacuum. At a given point and at a particular time the electric field is in the +x direction and the magnetic field is in the -y direction, and at that point the intensity of the wave is $0.45 \mathrm {~W} / \mathrm { m } ^ { 2 }$ $\left( c = 3.0 \times 10 ^ { 8 } \mathrm {~m} / \mathrm { s } \right.$ $\mu _ { 0 } = 4 \pi \times 10 ^ { - 7 } \mathrm {~T} \cdot \mathrm { m } / \mathrm { A } ,$ $\left. \varepsilon _ { 0 } = 8.85 \times 10 ^ { - 12 } \mathrm { C } ^ { 2 } / \mathrm { N } \cdot \mathrm { m } ^ { 2 } \right)$ 
(a) What is the direction of propagation of the wave?
(b) What is the electric field amplitude at the given point?

Accepted Answer

(a) -z dir

Question 4

A flat circular coil having 16 turns, each of diameter 20 cm, is in a uniform and steady 0.13-T magnetic field.
(a) Find the total magnetic flux through the coil when the field is perpendicular to the plane of the coil.
(b) If the coil is rotated in 10 ms so its plane is parallel to the field, find the average induced emf in the coil.

Accepted Answer

(a) 0.065

Question 5

A rectangular loop of wire that can rotate about an axis through its center is placed between the poles of a magnet in a magnetic field with a strength of 0.40 T, as shown in the figure. The length of the loop L is 0.16 m and its width w is 0.040 m. What is the magnetic flux through the loop when the plane of the loop makes an angle of 60° with the magnetic field?

Accepted Answer

A)  2.6 × 10-3 T ∙ m2 
B)  1.3 × 10-3 T ∙ m2 
C)  0 T ∙ m2 
D)  2.2 × 10-3 T ∙ m2 
E)  0.80 T ∙ m2 
A)  2.6 × 10-3 T ∙ m2 
B)  1.3 × 10-3 T ∙ m2 
C)  0 T ∙ m2 
D)  2.2 × 10-3 T ∙ m2 
E)  0.80 T ∙ m2

Question 6

As shown in the figure, two solenoids are in line. The switch S, initially closed, is suddenly opened. Just after opening S, what is the polarity of the induced emf in terminals X and Y?

Accepted Answer

A)  X and Y are at the same potential. 
B)  X is positive and Y is negative. 
C)  Y is positive and X is negative. 
A)  X and Y are at the same potential. 
B)  X is positive and Y is negative. 
C)  Y is positive and X is negative.

Question 7

A closed flat loop conductor with radius $2.0 \mathrm {~m}$ is located in a changing uniform magnetic field. If the emf induced in the loop is $2.0 \mathrm {~V}$ what is the rate at which the magnetic field strength is changing if the magnetic field is oriented perpendicular to the plane in which the loop lies?

Accepted Answer

A)  0.16 T/s 
B)  1.0 T/s 
C)  0.080 T/s 
D)  2.0 T/s 
A)  0.16 T/s 
B)  1.0 T/s 
C)  0.080 T/s 
D)  2.0 T/s

Question 8

At what rate are photons emitted by a 50.0-W sodium vapor lamp if it is producing monochromatic light of wavelength 589 nm? (c = 3.00 × 108 m/s, h = 6.626 × 10-34 J ∙ s)

Accepted Answer

1.48 × 10²⁰

Question 9

A cordless phone operates at 900 MHz. What is the wavelength of the electromagnetic wave used by this phone? (c = 3.0 × 108 m/s)

Accepted Answer

Question 10

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

Accepted Answer

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

Question 11

What is the photon energy of red light having a wavelength of 6.40 × 102 nm? (c = 3.00 × 108 m/s, h = 6.626 × 10-34 J ∙ s)

Accepted Answer

A)  1.13 × 10-19 J 
B)  1.31 × 10-19 J 
C)  3.11 × 10-19 J 
D)  1.94 × 10-19 J 
A)  1.13 × 10-19 J 
B)  1.31 × 10-19 J 
C)  3.11 × 10-19 J 
D)  1.94 × 10-19 J

Question 12

A circular coil of copper wire is lying flat on a horizontal table. A bar magnet is held above the center of the coil with its south pole downward. The magnet and the coil are now both raised upward with the same velocities. As viewed from above, what is the direction of the current induced in the coil as the magnet approaches the coil?

Accepted Answer

A)  counterclockwise 
B)  clockwise 
C)  No current is induced in the coil. 
D)  An emf but no current is induced in the coil. 
A)  counterclockwise 
B)  clockwise 
C)  No current is induced in the coil. 
D)  An emf but no current is induced in the coil.

Question 13

As shown in the figure, a uniform magnetic field B is confined to a cylindrical volume of radius 0.050 m. This field is directed into the plane of the page and is increasing at a constant rate of $0.900 \mathrm {~T} / \mathrm { s }$ Calculate the magnitude and direction (clockwise or counterclockwise) of the current induced in a circular wire ring of radius 0.16 m and resistance $7.1 \Omega$ that encircles the magnetic field region.

Accepted Answer

The answer of As shown in the figure, a uniform...

Question 14

A circular coil of 20 turns and radius 5.0 cm is placed with its plane oriented at 90° to a uniform magnetic field of $0.10 \mathrm {~T}$ The field is now increased at a steady rate, reaching a value of $0.50 \mathrm {~T}$ after 4.0 seconds. What emf is induced in the coil?

Accepted Answer

A)  0.016 V 
B)  0.021 V 
C)  0.026 V 
D)  0.031 V 
E)  0.036 V 
A)  0.016 V 
B)  0.021 V 
C)  0.026 V 
D)  0.031 V 
E)  0.036 V

Question 15

The cylindrical filament in a light bulb has a diameter of 0.050 mm, an emissivity of 1.0, and a temperature of 3000°C. How long should the filament be in order to radiate 60 W of power? (σ = 5.67 × 10-8 W/m2 ∙ K4)

Accepted Answer

A)  11 cm 
B)  9.4 cm 
C)  8.6 cm 
D)  7.2 cm 
E)  5.9 cm 
A)  11 cm 
B)  9.4 cm 
C)  8.6 cm 
D)  7.2 cm 
E)  5.9 cm

Question 16

A circular wire ring is situated above a long straight wire, as shown in the figure. The straight wire has a current I flowing to the right, and this current is increasing at a constant rate. Which of the following statements is true?

Accepted Answer

A)  There is an induced current in the wire ring, directed in clockwise orientation. 
B)  There is an induced current in the wire ring, directed in a counterclockwise orientation. 
C)  There is no induced current in the wire ring. 
A)  There is an induced current in the wire ring, directed in clockwise orientation. 
B)  There is an induced current in the wire ring, directed in a counterclockwise orientation. 
C)  There is no induced current in the wire ring.

Question 17

As the temperature of a blackbody increases, what happens to the peak wavelength of the light it radiates?

Accepted Answer

A)  It gets longer. 
B)  It gets shorter. 
C)  The wavelength is not affected by the temperature of the object. 
A)  It gets longer. 
B)  It gets shorter. 
C)  The wavelength is not affected by the temperature of the object.

Question 18

If the absolute temperature of an object is tripled, the thermal power radiated by this object (assuming that its emissivity and size are not affected by the temperature change) will

Accepted Answer

A)  increase by a factor of 3. 
B)  increase by a factor of 9. 
C)  increase by a factor of 18. 
D)  increase by a factor of 27. 
E)  increase by a factor of 81. 
A)  increase by a factor of 3. 
B)  increase by a factor of 9. 
C)  increase by a factor of 18. 
D)  increase by a factor of 27. 
E)  increase by a factor of 81.

Question 19

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?

Accepted Answer

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

Question 20

An FM radio station broadcasts at 96.7 MHz. What is the wavelength of the radio wave used for this broadcast? (c = 3.0 × 108 m/s)

Accepted Answer

Exam 25: EM Induction and Em Waves

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)

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

As shown in the figure, two solenoids are in line. The switch S, initially closed, is suddenly opened. Just after opening S, what is the polarity of the induced emf in terminals X and Y?

At what rate are photons emitted by a 50.0-W sodium vapor lamp if it is producing monochromatic light of wavelength 589 nm? (c = 3.00 × 108 m/s, h = 6.626 × 10-34 J ∙ s)

A cordless phone operates at 900 MHz. What is the wavelength of the electromagnetic wave used by this phone? (c = 3.0 × 108 m/s)

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

What is the photon energy of red light having a wavelength of 6.40 × 102 nm? (c = 3.00 × 108 m/s, h = 6.626 × 10-34 J ∙ s)

A circular coil of 20 turns and radius 5.0 cm is placed with its plane oriented at 90° to a uniform magnetic field of 0.10 T0.10 \mathrm {~T}0.10 T The field is now increased at a steady rate, reaching a value of 0.50 T0.50 \mathrm {~T}0.50 T after 4.0 seconds. What emf is induced in the coil?

The cylindrical filament in a light bulb has a diameter of 0.050 mm, an emissivity of 1.0, and a temperature of 3000°C. How long should the filament be in order to radiate 60 W of power? (σ = 5.67 × 10-8 W/m2 ∙ K4)

A circular wire ring is situated above a long straight wire, as shown in the figure. The straight wire has a current I flowing to the right, and this current is increasing at a constant rate. Which of the following statements is true?

As the temperature of a blackbody increases, what happens to the peak wavelength of the light it radiates?

If the absolute temperature of an object is tripled, the thermal power radiated by this object (assuming that its emissivity and size are not affected by the temperature change) will

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?

An FM radio station broadcasts at 96.7 MHz. What is the wavelength of the radio wave used for this broadcast? (c = 3.0 × 108 m/s)

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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)

At what rate are photons emitted by a 50.0-W sodium vapor lamp if it is producing monochromatic light of wavelength 589 nm? (c = 3.00 × 10⁸ m/s, h = 6.626 × 10^-34 J ∙ s)

A cordless phone operates at 900 MHz. What is the wavelength of the electromagnetic wave used by this phone? (c = 3.0 × 10⁸ m/s)

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

What is the photon energy of red light having a wavelength of 6.40 × 10² nm? (c = 3.00 × 10⁸ m/s, h = 6.626 × 10^-34 J ∙ s)

A circular coil of 20 turns and radius 5.0 cm is placed with its plane oriented at 90° to a uniform magnetic field of $0.10 \mathrm {~T}$ The field is now increased at a steady rate, reaching a value of $0.50 \mathrm {~T}$ after 4.0 seconds. What emf is induced in the coil?

The cylindrical filament in a light bulb has a diameter of 0.050 mm, an emissivity of 1.0, and a temperature of 3000°C. How long should the filament be in order to radiate 60 W of power? (σ = 5.67 × 10^-8 W/m² ∙ K⁴)

An FM radio station broadcasts at 96.7 MHz. What is the wavelength of the radio wave used for this broadcast? (c = 3.0 × 10⁸ m/s)