Chapter 22: Electromagnetic Waves
Practice Questions


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.  

As a capacitor charges
there is an electric current through the capacitor.
There is no electric current flowing in the circuit until the capacitor is fully charged.
There is a displacement current between the plates of the capacitor.

19.  

A 10 volt battery is connected to a switch, a 35 microF capacitor and a 120 ohm resistor. Two milliseconds after the switch is closed, what is the voltage on the capacitor?
1.2 V
2.8 V
3.8 V
10 V

20.  

What is Maxwell's displacement current inside the capacitor in the previous question at 2 ms?
16 mA
20 mA
57 mA
0 A

21.  

What is the rate of change of the electric flux in the capacitor in question 19?
2 x 10 5 V/m3
2000 V/m3
2.7 x 10 20 V/m3
5.9 x 10 9 V/m3


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