Last updated: November 2, 2008
PHY 2054 Discussion – Fall ‘08
Practice Exam Problems (Chapter 21)
1.
Maxwell developed his theory of electromagnetism by combining previous discoveries. He added his
own original hypothesis that: (Maxwell’s Prediction)
moving electric charges produce magnetic fields
a. electric charges produce electric fields
b.
c. changing electric fields produce magnetic fields
c. changing magnetic fields produce electric fields
2.
A radar pulse returns 3.0×10-4 seconds after it is sent out, having been reflected by an object. What is
the distance between the radar antenna and the object? (Speed of Electromagnetic Wave)
a. 9.0×10 4
m b. 4.5×104 m c. 6.0×104 m d. 1.0×104 m
3.
An ultraviolet light wave has a wavelength of 300 nm and speed of 2.1×10 8 m/s through a transparent
medium. What is the frequency of this wave in the medium? (Wave Equation)
9.0×102 Hz
4.
c. 7.0×1014 Hz
a. 6.3×10 2 Hz
b.
c. 10×1014 Hz
The Earth is 1.49×1011 m from the Sun. If the solar radiation at the top of the Earth’s atmosphere is 1
340 W/m2, what is the total power output of the Sun? (Intensity of Spherical Waves)
a. 7.48×10 27
W b. 2.34×1030 W c. 6.62×1026 W d. 3.74×1026 W
5.
In order of increasing frequency, which of the following is correct? (Spectrum of Electromagnetic
Waves)
a. visible, radio, ultraviolet and x-ray b. infrared, visible, ultraviolet and gamma
c.
visible, gamma, ultraviolet and x-ray d. infrared x-ray, visible and gamma
6.
An observer is moving in space toward a distant star at 100 km/s while the star is moving toward the
observer at 200 km/s; the relative velocity being 300 km/s of approach. What relative change in
frequency of the light from the star as seen by the observer? (Doppler Effect)
0.10 % decrease
Answers: 1-c
2-b
c. 0.067% increase
3-c
4-d
5-b
6-a
d. 0.033% decrease
a. 0.10 % increase
b.