MODULE 12 Problem Set Twelve 1. Index of refraction is defined as the speed of l

Question

MODULE 12
Problem Set Twelve

1. Index of refraction is defined as the speed of light in a vacuum divided by the speed of light in the medium. What is the index of refraction for glass? Speed of light c = 3.0 x 108 m/s. Speed of light in glass = 2.0 x 108 m/s.

2. Using the definition above, what is the index of refraction for diamond? Speed of light in diamond = 1.24 x 108 m/s.

3. The index of refraction for the compound benzene is 1.50. What is the speed of light in benzene?

4. A beam of light is reflected at an angle of 15° from the normal. What was the incident angle of the beam of light?

5. A radio station broadcasts at 550 kHz (550,000 cycles per sec). What is the wavelength of this signal?

6. A light beam has a frwuency of 5 x 1015 Hz. What is its wavelength?

7. When a "full" moon rises, the size appears to be larger than when it is directly overhead. Why?

8. When the "full" moon rises, the color is yellowish while its color directly overhead is white. Why?

9. A certain radar installation transmits electromagnetic radiation with a wavelength of 2.5 cm. What is the frequency of this radiation?

10. For the radar in #9 above, how many seconds will it take for a signal to reach an airplane 15 km away, and return to the radar installation?

Explanation / Answer

1)

Index of refraction = (3.0 x 10^8)/(2.0 x 10^8) = 1.5

2)

2. c = (3.0 x 10^8)/(1.24 x 10^8) = 2.42 x 10^8 m/s

3)

c = (3.0 x 10^8)/(1.50)= 2.0 x 10^8 m/s

4)

Incident angle = 15 degree

5)

= c/f = 3*10^8/550*10^3= 545.45m

6)

= c/f = 3*10^8/5*10^15 = 0.6*10^-7= 60nm

7)

Because its closer to the horizon giving the illusion it is larger; the relative distance to objects on the horizon are much closer then when overhead.

8)

Because of Refraction of light

9)

f = c / wavelength = 3*10^8 / 2.5*10^-2 = 12 GHz

10)

Time = Distance / speed = (2 x 15000) /( 3 x 10^8) = 0.1 ms

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