# hw2 - red light into a green one The judge says “I...

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AS 117: DISCUSSION SECTION — Homework No. 2 Electromagnetic Radiation and the Forces of Nature The goal of these exercises is for you to develop a feeling for the quantitative aspects of electromagnetic radiation as well as to gain some insight regarding the interplay between the four forces of nature. Note that these simple arithmetical calculations are intended to clarify, not to muddy these concepts so please consult with either your TA or Professor Bania regarding any and all aspects of these problems. .. 1. The Dopper radar that the Massachusetts State Police use to catch you speeding operates in the X-band wavelength band. (Actually your microwave oven transmits microwaves in this same band.) The center of X-band is 3 cm. What frequency is transmitted by the police radar? 2. You have been stopped for running a red traFc light in a small town in Maine. Having gotten an ‘A’ in AS 117, you tell the judge that the Doppler Shift, caused by your car’s speed with respect to the stop light, had changed the
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Unformatted text preview: red light into a green one. The judge says: “I understand all about blueshifts, so I accept your explanation. However, I ±nd you guilty of another charge.” How fast (in MILES PER HOUR [mph]) would you need to be approaching the traFc light to blueshift a red light into a green one? What was the charge you were convicted of? 3. Since your car was approaching the traFc light, why is it that the light’s radiation was blueshifted? In fact, was it? 4. When you sit in your chair during AS 117 lectures, which of the four forces of Nature is it that keeps you from falling into the basement, en route to the center of the Earth? Which are the two forces being balanced to produce your stationary, yet supremely attentive, state? Solutions due in section 1 week from today. Wavelength of RED light = 6500 Angstroms Wavelength of GREEN light = 5000 Angstroms Speed of light = c = 3 × 10 5 km sec-1 = 186,210 miles per second...
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