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===== Doppler Effect: Instructor's Guide =====

==== Main Ideas ====

  - Using hyperbolic triangle trig to derive an important consequence of special relativity.

==== Students' Task ====
//Estimated Time: 10 minutes, including wrap-up//

Consider an inertial observer moving to the right in the laboratory frame who
is carrying a flashlight that is pointing to the left.  Suppose the moving
observer turns on the flashlight just long enough to emit one complete
wavelength of light.  What wavelength is seen in the laboratory frame?

==== Prerequisite Knowledge ====

  * basic understanding of special relativity
  * basic understanding of hyperbolic triangle trig

==== Props/Equipment ====

  * [[props:start#whiteboards|Table top whiteboards]] and markers

==== Wrap-Up ====

  * Using student work if possible, show how to solve this problem using hyperbolic triangle trig.

See also the discussion in [[gsr>book:gsr:doppler|the text]].