Question 1

In an unpolarized EM wave, the electric field direction is

Accepted Answer

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. 
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.

Question 2

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?

Accepted Answer

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 
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

Question 3

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?

Accepted Answer

A)  32 V/m 
B)  16 V/m 
C)  8.0 V/m 
D)  4.0 V/m 
E)  2.0 V/m 
A)  32 V/m 
B)  16 V/m 
C)  8.0 V/m 
D)  4.0 V/m 
E)  2.0 V/m

Question 4

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?

Accepted Answer

A)  elliptical 
B)  linear 
C)  circular 
D)  unpolarized 
E)  more than one of the above 
A)  elliptical 
B)  linear 
C)  circular 
D)  unpolarized 
E)  more than one of the above

Question 5

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

Accepted Answer

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. 
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.

Question 6

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

Accepted Answer

A)  1 ms 
B)  1 μs 
C)  1 ns 
D)  1 ps 
E)  1 fs 
A)  1 ms 
B)  1 μs 
C)  1 ns 
D)  1 ps 
E)  1 fs

Question 7

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

Accepted Answer

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 
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

Question 8

Radio waves were discovered by

Accepted Answer

A)  Hertz. 
B)  Maxwell. 
C)  Penzias. 
D)  Dumont. 
E)  Marconi. 
A)  Hertz. 
B)  Maxwell. 
C)  Penzias. 
D)  Dumont. 
E)  Marconi.

Question 9

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?

Accepted Answer

A)  22 m 
B)  6.3 m 
C)  30 m 
D)  40 m 
A)  22 m 
B)  6.3 m 
C)  30 m 
D)  40 m

Question 10

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?

Accepted Answer

A)  0.50 I0 
B)  0.35 I0 
C)  0.25 I0 
D)  0.13 I0 
E)  0 
A)  0.50 I0 
B)  0.35 I0 
C)  0.25 I0 
D)  0.13 I0 
E)  0

Question 11

The highest frequency in visible light is associated with the color

Accepted Answer

A)  red. 
B)  orange. 
C)  green. 
D)  blue. 
E)  violet. 
A)  red. 
B)  orange. 
C)  green. 
D)  blue. 
E)  violet.

Question 12

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?

Accepted Answer

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 
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

Question 13

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.

Accepted Answer

A)  1/2 the distance 
B)  1/8 the distance 
C)  1/4 the distance 
D)  1/16 the distance 
A)  1/2 the distance 
B)  1/8 the distance 
C)  1/4 the distance 
D)  1/16 the distance

Question 14

How far does light travel in a century?

Accepted Answer

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 
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

Question 15

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

Accepted Answer

A)  0 
B)  0.5 
C)  1 
D)  just less than 1 
E)  (1/2)1/2 
A)  0 
B)  0.5 
C)  1 
D)  just less than 1 
E)  (1/2)1/2

Question 16

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?

Accepted Answer

A)  600 nm 
B)  900 nm 
C)  400 nm 
D)  1.35 × 103 nm 
E)  267 nm 
A)  600 nm 
B)  900 nm 
C)  400 nm 
D)  1.35 × 103 nm 
E)  267 nm

Question 17

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?

Accepted Answer

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 
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

Question 18

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

Accepted Answer

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. 
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.

Exam 22: Electromagnetic Waves

In an unpolarized EM wave, the electric field direction is

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?

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?

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

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

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

Radio waves were discovered by

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?

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?

The highest frequency in visible light is associated with the color

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?

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.

How far does light travel in a century?

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

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?

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?

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

Introduction

Motion Along a Line

Motion in a Plane

Force and Newtons Laws of Motion

Circular Motion

Conservation of Energy

Linear Momentum

Torque and Angular Momentum

Fluids

Elasticity and Oscillations

Waves

Sound

Temperature and the Ideal Gas

Heat

Thermodynamics

Electric Forces and Fields

Electric Potential

Electric Current and Circuits

Magnetic Forces and Fields

Electromagnetic Induction

Alternating Current

Reflection and Refraction of Light

Optical Instruments

Interference and Diffraction

Relativity

Early Quantum Physics and the Photon

Quantum Physics

Nuclear Physics

Particle Physics

Filters

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?