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Mon 17 Mar, 2014 04:44 pm
I was watching the Big Bang Theory last night and Sheldon was dressed as the Doppler Effect. I was explaining to my daughter what that was. However, later, as I was lying in bed thinking about it, I realized I had a fundamental misunderstanding. It revolves around the usual discussion of a train whistle and the frequency that you hear as the train approaches.
The pitch is described as increasing (and that is in fact what you hear). However, if the train is moving at a constant velocity (call it x) and the frequency of the whistle is constant (call it y), then wouldn't the frequency perceived by the observer be constant at x+y? What would make it increase?
@mattstoc,
No. First of all, it doesn't make sense to add a velocity to a frequency. Those two quantities are not measuring the same thing, so adding them together doesn't make sense.
@maxdancona,
Picture if you are in boat in a lake with waves going from north to south. Imagine that a boat that is tied to a moor (not moving compared to the water) will go up and down once each 5 seconds due to the waves.
Now start the engine and move north.... do you think the boat will go up and down more often (due the waves) or less often?
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