This question will look at what happens when an observer moves towards a stationary source emitting electromagnetic waves of frequency f, and speed c.
a. a First consider the observer to be stationary.
- i How many wavefronts will the observer receive in 1 s?
- ii How much time will it take for the next wavefront to arrive at the observer?
- iii How far apart—distance-wise—will the wavefronts be?
b. b Now consider the observer moving towards the source at a speed v.
- i Will it take the same time, less time or more time for the observer to receive another wavefront than your answer to part a ii?
- ii Justify your answer to part i.
- iii So, will the observer now observe waves with the same frequency, a smaller frequency or a larger frequency than before?
- iv And will the observer now observe waves with the same wavelength, a smaller wavelength or a larger wavelength than before?