Doppler effect in light (moving observer):
https://www.youtube.com/watch?v=bg7O4rtlwEE
The speed of the light pulses as measured by the stationary observer is
c = df
where d is the distance between the pulses and f is the frequency measured by the stationary observer. The speed of the pulses as measured by the moving observer is
c'= df' c
where f' f is the frequency measured by the moving observer.
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