How to prove the doppler effect for light wave? Isn't that the speed of light is constant for both the observer and source? If the wavelength for both the source and observer is the same, then the frequency is the same too, so there is no doppler effect? If the wavelength is different, but if we use Lorren's transfer, the new wave obtained will be the same if the observe is moving towards or leaving the source! How to deal with this?