Chapter 25: Electromagnetic Waves
Practice Questions



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1.  


The above figure represents an electromagnetic wave frozen in time. The blue line is the
frequency.
wavelength.
period.

2.  

If the wavelength of the wave in the above question is 3x10-5m the wave is
a radio wave.
a microwave.
an infrared wave.
visible light wave.
UV wave.
X-ray.

3.  

If the wavelength of the wave in question 1 is 3 nm the wave is
a radio wave.
a microwave.
an infrared wave.
visible light wave.
UV wave.
X-ray.

4.  

If the wavelength of the wave in question 1 is 0.6 microns the wave is
a radio wave.
a microwave.
an infrared wave.
visible light wave.
UV wave.
X-ray.

5.  

If the wavelength of the wave in question 1 is 10 km the wave is
a radio wave.
a microwave.
an infrared wave.
visible light wave.
UV wave.
X-ray.

6.  

In the figure an electromagnetic wave is shown moving left to right. If the number in the upper right is the time measured in units of 100ps the wave is a
a radio wave.
a microwave.
visible light wave.
UV wave.
X-ray.

7.  

What is the wavelength of wave in question 6?
1 cm.
1 meter.
4 meters.
15 meters.
1 km.

8.  

If the time counter in question 6 is clicking time in units of 0.2fs the wave is
a radio wave.
a microwave.
an infrared wave.
visible light wave.
X-ray.
None of the above

9.  

The wavelength of the wave in question 8 is
10 m.
1.5 mm.
.4 microns.
6x10-10 m.

10.  

If the counter in question 6 is counting in seconds the wave is
a radio wave.
a microwave.
an infrared wave.
UV wave.
none of the above

11.  

What would be the wavelength of the wave in question 10?
2000 m
10 km
2.5x104 km
3.0x106 km

12.  

If the electric vector in the E & M wave has a maximum value of 1000 V/m what is the value for the maximum of the magnetic vector?
1.3 x 10 -6 T
2.3 x 10 -6 T
3.3 x 10 -6 T
4.3 x 10 -6 T

13.  

What is the energy density (energy per cubic meter) in a small region of space in the above wave at an instant of time when the electric vector is a maximum?
4.425x10-6 J/m3
8.85x10-9 J/m3
8.85x10-6 J/m3
1.77x10-6 J/m3

14.  

What is the energy density (energy per cubic meter) carried by the magnetic field vector in a small region of space in the above wave at an instant of time when the electric vector is a maximum?
1.77x10-5 J/m3
3 x 10 -6 J/m3
9 x 10 -9 J/m3
4.425x10-6 J/m3

15.  

What is the average intensity of the E & M wave in question 12 ?
2655 W/m2
5310 W/m2
1328 W/m2
3 W/m2

16.  

On a very clear day in summer the solar intensity in the 'little lattitudes' might reach 1000 W/m2 (averaged over time). What would be the maximum value for the electric vector?
870 V/m
1750 V/m
750 V/m
250 V/m

17.  

What is the (maximum) magnetic field vector in the above question?
1 x 10 -6 T
2 x 10 -6 T
3 x 10 -6 T
4 x 10 -6 T

18.  

Unpolarized light with intensity Iofalls on a polaroid sheet, the transmitted intensity is
Io/2
Io/4
Io/8
Io/16

19.  

If the axis of the polarizer in the previous question is vertical a second one is placed at 45o what will be the resulting intensity?
Io/2
Io/4
Io/8
Io/16

20.  

A third polaroid is added after the 45o one, its axis is horizontal, what is the resulting intensity?
Io/2
Io/4
Io/8
Io/16

21.  

The 45o polaroid is moved from between the vertical and horizontal polaroid to after the horizontal one, what is the resulting intensity?
Io/2
Io/4
Io/8
Io/16
zero

22.  

A 1000000 m2 solar sail is used to propel a small spaceship. If light from the previous question is reflecting off the sail what is the force exerted on the sail?
8.85 N
125 N
1000 N
1255 N

23.  

If the space ship in the above question has a mass of 1000 kg, how far would it travel in one month?
30000 m
3x106 m
3x108 m
3x1010 m
3x1016 m

24.  

An electromagnetic wave has an electric vector with a maximum value of 1000 V/m, what is the average magnitude of the Intensity?
312 W/m2
1312 W/m2
1328
1600 W/m2


Practice Questions: Practice Questions by Carl Adler, East Carolina University. ©2002 by Prentice Hall, Inc.


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