Doppler effect = effect on frequency when source and receiver are moving relative to each other:
Doppler effect = effect on frequency when source and receiver are moving relative to each other:
Suppose a source, say a star, moves toward the astronomer with velocity V. The astronomer observes a pulse of N waves in time tA and notes that the distance between the front and the end of the the pulse is ctA - VtA and since there are N waves in it, the wave-length must be
In the frame of the start on the other hand, the pulse is emitted in proper time tS and