Question 1

If the electric field in a plane electromagnetic wave is given by Emsin[(3 *106 m-1 x) -$ \omega $t], the value of $ \omega $is:

Accepted Answer

A)  0.01 rad/s 
B)  10 rad/s 
C)  100 rad/s 
D)  9*1014 rad/s 
E)  9 *1016 rad/s 
A)  0.01 rad/s 
B)  10 rad/s 
C)  100 rad/s 
D)  9*1014 rad/s 
E)  9 *1016 rad/s

Question 2

The product µ0ε0 has the same units as:

Accepted Answer

A)  (velocity)2 
B)  (velocity)1/2 
C)  1/velocity 
D)  1/velocity2 
E)  1/velocity1/2 
A)  (velocity)2 
B)  (velocity)1/2 
C)  1/velocity 
D)  1/velocity2 
E)  1/velocity1/2

Question 3

A pole stands in a river, half in and half out of the water. Another pole of the same length stands vertically on the shore at a place where the ground is level. The shadow cast by the pole in the river on the river bottom is:

Accepted Answer

A)  slightly longer than the shadow of the pole on land 
B)  much longer than the shadow of the pole on land 
C)  shorter than the shadow of the pole on land 
D)  shorter than the shadow of the pole on land if the sun is high and longer if the sun is low 
E)  the same length as the shadow of the pole on land 
A)  slightly longer than the shadow of the pole on land 
B)  much longer than the shadow of the pole on land 
C)  shorter than the shadow of the pole on land 
D)  shorter than the shadow of the pole on land if the sun is high and longer if the sun is low 
E)  the same length as the shadow of the pole on land

Question 4

Visible light has a frequency of about:

Accepted Answer

A)  5 *1018 Hz 
B)  5 * 1016 Hz 
C)  5 * 1014 Hz 
D)  5 * 1012 Hz 
E)  5 *1010 Hz 
A)  5 *1018 Hz 
B)  5 * 1016 Hz 
C)  5 * 1014 Hz 
D)  5 * 1012 Hz 
E)  5 *1010 Hz

Question 5

Maxwell's equations predict that the speed of electromagnetic waves in free space is given by:

Accepted Answer

A)  µ0ε0 
B)  (µ0ε0)1/2 
C)  1/ µ0ε0 
D)  1/(µ0ε0)1/2 
E)  1/(µ0ε0)2 
A)  µ0ε0 
B)  (µ0ε0)1/2 
C)  1/ µ0ε0 
D)  1/(µ0ε0)1/2 
E)  1/(µ0ε0)2

Question 6

The rectangular metal tank shown is filled with an unknown liquid. The observer, whose eye is level with the top of the tank, can just see corner E. The index of refraction of this liquid is:

Accepted Answer

A)  1.75 
B)  1.67 
C)  1.50 
D)  1.33 
E)  1.25 
A)  1.75 
B)  1.67 
C)  1.50 
D)  1.33 
E)  1.25

Question 7

At a certain point and a certain time the electric field of an electromagnetic wave is in the negative z direction and the magnetic field is in the positive y direction. Which of the following statements is true?

Accepted Answer

A)  Energy is being transported in the positive x direction but half a cycle later, when the electric field is in the opposite direction, it will be transported in the negative x direction. 
B)  Energy is being transported in the positive x direction and half a cycle later, when the electric field is in the opposite direction, it will still be transported in the positive x direction. 
C)  Energy is being transported in the negative x direction but half a cycle later, when the electric field is in the opposite direction, it will be transported in the positive x direction. 
D)  Energy is being transported in the negative x direction and half a cycle later, when the electric field is in the opposite direction, it will still be transported in the negative x direction. 
E)  None of the above is true. 
A)  Energy is being transported in the positive x direction but half a cycle later, when the electric field is in the opposite direction, it will be transported in the negative x direction. 
B)  Energy is being transported in the positive x direction and half a cycle later, when the electric field is in the opposite direction, it will still be transported in the positive x direction. 
C)  Energy is being transported in the negative x direction but half a cycle later, when the electric field is in the opposite direction, it will be transported in the positive x direction. 
D)  Energy is being transported in the negative x direction and half a cycle later, when the electric field is in the opposite direction, it will still be transported in the negative x direction. 
E)  None of the above is true.

Question 8

The rate of energy transport of an electromagnetic wave per unit area is given by:

Accepted Answer

A)  the vector 
B)  the Poynting vector 
C)  the Poynting vector divided by the area 
D)  the Poynting vector divided by time 
E)  the Poynting vector multiplied by time 
A)  the vector 
B)  the Poynting vector 
C)  the Poynting vector divided by the area 
D)  the Poynting vector divided by time 
E)  the Poynting vector multiplied by time

Question 9

A sinusoidal electromagnetic wave has an electric field whose rms value is 100 V/m. What is the instantaneous rate S of energy flow for this wave?

Accepted Answer

A)  1.7 *10-4 W/m2 
B)  13 W/m2 
C)  27 W/m2 
D)  1.0 *105 W/m2 
E)  4.0*1010 W/m2 
A)  1.7 *10-4 W/m2 
B)  13 W/m2 
C)  27 W/m2 
D)  1.0 *105 W/m2 
E)  4.0*1010 W/m2

Question 10

In a plane electromagnetic wave in vacuum, the ratio E/B of the amplitudes in SI units of the two fields is:

Accepted Answer

A)  the speed of light 
B)  an increasing function of frequency 
C)  a decreasing function of frequency 
D)    
E)    
A)  the speed of light 
B)  an increasing function of frequency 
C)  a decreasing function of frequency 
D)    
E)

Question 11

The index of refraction for diamond is 2.5. Which of the following is correct for the situation shown?

Accepted Answer

A)  (sin a)/(sin b) = 2.5 
B)  (sin b)/(sin d) = 2.5 
C)  (cos a)/(cos c) = 2.5 
D)  (sin a)/(sin c) = 1/(2.5) 
E)  a/c = 2.5 
A)  (sin a)/(sin b) = 2.5 
B)  (sin b)/(sin d) = 2.5 
C)  (cos a)/(cos c) = 2.5 
D)  (sin a)/(sin c) = 1/(2.5) 
E)  a/c = 2.5

Question 12

An electromagnetic wave is traveling in the positive x direction with its electric field along the z axis and its magnetic field along the y axis. The fields are related by:

Accepted Answer

A)   $\partial$ E/ $\partial$ x = $\mu$0$\varepsilon$0 $\partial$ B/ $\partial$ x 
B)   $\partial$ E/ $\partial$ x = $\mu$0$\varepsilon$0 $\partial$ B/ $\partial$ t 
C)   $\partial$ B/ $\partial$ x = $\mu$0$\varepsilon$0 $\partial$ E/ $\partial$ x 
D)   $\partial$ B/ $\partial$ x = $\mu$0$\varepsilon$0 $\partial$ E/ $\partial$ t 
E)   $\partial$ B/ $\partial$ x = -$\mu$0$\varepsilon$0 $\partial$ E/ $\partial$ t 
A)   $\partial$ E/ $\partial$ x = $\mu$0$\varepsilon$0 $\partial$ B/ $\partial$ x 
B)   $\partial$ E/ $\partial$ x = $\mu$0$\varepsilon$0 $\partial$ B/ $\partial$ t 
C)   $\partial$ B/ $\partial$ x = $\mu$0$\varepsilon$0 $\partial$ E/ $\partial$ x 
D)   $\partial$ B/ $\partial$ x = $\mu$0$\varepsilon$0 $\partial$ E/ $\partial$ t 
E)   $\partial$ B/ $\partial$ x = -$\mu$0$\varepsilon$0 $\partial$ E/ $\partial$ t

Question 13

Select the correct statement:

Accepted Answer

A)  ultraviolet light has a longer wavelength than infrared 
B)  blue light has a higher frequency than X rays 
C)  radio waves have a higher frequency than gamma rays 
D)  gamma rays have a higher frequency than infrared waves 
E)  electrons are a type of electromagnetic wave 
A)  ultraviolet light has a longer wavelength than infrared 
B)  blue light has a higher frequency than X rays 
C)  radio waves have a higher frequency than gamma rays 
D)  gamma rays have a higher frequency than infrared waves 
E)  electrons are a type of electromagnetic wave

Question 14

The diagrams show four pairs of polarizing sheets, with the polarizing directions indicated by dashed lines. The two sheets of each pair are placed one behind the other and the front sheet is illuminated by unpolarized light. The incident intensity is the same for all pairs of sheets. Rank the pairs according to the intensity of transmitted light, least to greatest.

Accepted Answer

A)  1, 2, 3, 4 
B)  4, 2, 1, 3 
C)  2, 4, 3, 1 
D)  2, 4, 1, 3 
E)  3, 1, 4, 2 
A)  1, 2, 3, 4 
B)  4, 2, 1, 3 
C)  2, 4, 3, 1 
D)  2, 4, 1, 3 
E)  3, 1, 4, 2

Question 15

The critical angle for total internal reflection at a diamond-air interface is 25 $\degree$ Suppose light is incident at an angle of $\theta$with the normal. Total internal reflection will occur if the incident medium is:

Accepted Answer

A)  air and $\theta$= 25 $\degree$ 
B)  air and $\theta$> 25 $\degree$ 
C)  air and$\theta$ 25 $\degree$ 
A)  air and $\theta$= 25 $\degree$ 
B)  air and $\theta$> 25 $\degree$ 
C)  air and$\theta$ 25 $\degree$

Question 16

Radio waves differ from visible light waves in that radio waves:

Accepted Answer

A)  travel slower 
B)  have a higher frequency 
C)  travel faster 
D)  have a lower frequency 
E)  require a material medium 
A)  travel slower 
B)  have a higher frequency 
C)  travel faster 
D)  have a lower frequency 
E)  require a material medium

Question 17

The order of increasing wavelength for blue (b), green (g), red (r), and yellow (y) light is:

Accepted Answer

A)  r, y, g, b 
B)  r, g, y, b 
C)  g, y, b, r 
D)  b, g, y, r 
E)  b, y, g, r 
A)  r, y, g, b 
B)  r, g, y, b 
C)  g, y, b, r 
D)  b, g, y, r 
E)  b, y, g, r

Question 18

For an electromagnetic wave the direction of the vector gives:

Accepted Answer

A)  the direction of the electric field 
B)  the direction of the magnetic field 
C)  the direction of wave propagation 
D)  the direction of the electromagnetic force on a proton 
E)  the direction of the emf induced by the wave 
A)  the direction of the electric field 
B)  the direction of the magnetic field 
C)  the direction of wave propagation 
D)  the direction of the electromagnetic force on a proton 
E)  the direction of the emf induced by the wave

Question 19

An unpolarized beam of light has intensity I0. It is incident on two ideal polarizing sheets. The angle between the axes of polarization of these sheets is $\theta$. Find $\theta$if the emerging light has intensity I0/4:

Accepted Answer

A)  sin-1(1/2) 
B)  sin-1(1/) 
C)  cos-1(1/2) 
D)  cos-1(1/) 
E)  tan-1(1/4) 
A)  sin-1(1/2) 
B)  sin-1(1/) 
C)  cos-1(1/2) 
D)  cos-1(1/) 
E)  tan-1(1/4)

Question 20

A point source emits electromagnetic energy at a rate of 100 W. The intensity 10 m from the source is:

Accepted Answer

A)  10 W/m2 
B)  1.6 W/m2 
C)  1.0 W/m2 
D)  0.080 W/m2 
E)  0.024W/m2 
A)  10 W/m2 
B)  1.6 W/m2 
C)  1.0 W/m2 
D)  0.080 W/m2 
E)  0.024W/m2

Exam 33: Electromagnetic Waves

If the electric field in a plane electromagnetic wave is given by Emsin[(3 *106 m-1 x) - ω \omega ω t], the value of ω \omega ω is:

The product µ0ε0 has the same units as:

A pole stands in a river, half in and half out of the water. Another pole of the same length stands vertically on the shore at a place where the ground is level. The shadow cast by the pole in the river on the river bottom is:

Visible light has a frequency of about:

Maxwell's equations predict that the speed of electromagnetic waves in free space is given by:

The rectangular metal tank shown is filled with an unknown liquid. The observer, whose eye is level with the top of the tank, can just see corner E. The index of refraction of this liquid is:

At a certain point and a certain time the electric field of an electromagnetic wave is in the negative z direction and the magnetic field is in the positive y direction. Which of the following statements is true?

The rate of energy transport of an electromagnetic wave per unit area is given by:

A sinusoidal electromagnetic wave has an electric field whose rms value is 100 V/m. What is the instantaneous rate S of energy flow for this wave?

In a plane electromagnetic wave in vacuum, the ratio E/B of the amplitudes in SI units of the two fields is:

The index of refraction for diamond is 2.5. Which of the following is correct for the situation shown?

An electromagnetic wave is traveling in the positive x direction with its electric field along the z axis and its magnetic field along the y axis. The fields are related by:

Select the correct statement:

The critical angle for total internal reflection at a diamond-air interface is 25 °\degree° Suppose light is incident at an angle of θ\thetaθ with the normal. Total internal reflection will occur if the incident medium is:

Radio waves differ from visible light waves in that radio waves:

The order of increasing wavelength for blue (b), green (g), red (r), and yellow (y) light is:

For an electromagnetic wave the direction of the vector gives:

An unpolarized beam of light has intensity I0. It is incident on two ideal polarizing sheets. The angle between the axes of polarization of these sheets is θ\thetaθ . Find θ\thetaθ if the emerging light has intensity I0/4:

A point source emits electromagnetic energy at a rate of 100 W. The intensity 10 m from the source is:

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If the electric field in a plane electromagnetic wave is given by E_msin[(3 *10⁶ m^-1 x) - $\omega$ t], the value of $\omega$ is:

The product µ₀ε₀ has the same units as:

The index of refraction for diamond is 2.5. Which of the following is correct for the situation shown? $The index of refraction for diamond is 2.5. Which of the following is correct for the situation shown?$

The critical angle for total internal reflection at a diamond-air interface is 25 $\degree$ Suppose light is incident at an angle of $\theta$ with the normal. Total internal reflection will occur if the incident medium is:

An unpolarized beam of light has intensity I₀. It is incident on two ideal polarizing sheets. The angle between the axes of polarization of these sheets is $\theta$ . Find $\theta$ if the emerging light has intensity I₀/4: