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Contracting Wavelength via mirrors.

  1. Aug 13, 2011 #1
    Suppose we had two perfectly parallel and reflecting mirrors located 10000 meters apart in a vacuum. A radio wave with wavelength 3 meters is emitted at the center first mirror in the direction of the center second mirror for exactly 10 nanoseconds (the overall length of the wave would be 3 meters). The object which emitted light at the first mirror is then removed no later than 25000 nanoseconds after emission. We would now have a wave of light 3 meters long continuously bouncing between these two mirrors.

    Now suppose that while the radio wave is bouncing between the mirrors, we contract the length between the mirrors to 0.003 meters, which is 1/1000 the wavelength of the radio wave itself. What happens to the radio wave? Does the wavelength itself contract to 0.003 (infrared range)? Does the radio wave escape its "container" or does the wave continue to exist as is but in a complicated self-interference pattern?
    Last edited: Aug 13, 2011
  2. jcsd
  3. Aug 13, 2011 #2


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    Two issues:

    1. Your radio impulse is very short: just one wavelength. Such impulse (what's its shape? Rectangular? Gaussian? Other?) has very wide spectrum, so you can't speak about its well defined frequency.

    2. As you compress the container in which radio impulse (or stationary wave) bounces, you reduce its wavelength/increase frequency. You may analyse this phenomenon in terms of Doppler's effect, or in terms of photon gaining energy while bouncing from moving mirror in the same manner as tennis ball gains energy when hit by a rocket.
  4. Aug 13, 2011 #3
    Although I've always known of the causes and effects of the Doppler effect, I'm surprised I didn't answer this question myself. For the tenth time this week, my interpretation of physical phenomena just made a right turn into hyperspace!
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