The observer starts moving relative to the emitter in Doppler:
https://www.youtube.com/watch?v=bg7O4rtlwEE
The frequency and the speed of the light pulses VARY PROPORTIONALLY for the moving observer, in violation of Einstein's relativity. The wavelength (or distance between subsequent pulses) obviously remains constant:
"Thus, the moving observer sees a wave possessing the same wavelength [...] but a different frequency [...] to that seen by the stationary observer."
http://farside.ph.utexas.edu/teachin...ml/node41.html
"Vo is the velocity of an observer moving towards the source. This velocity is independent of the motion of the source. Hence, the velocity of waves relative to the observer is c + Vo. [...] The motion of an observer does not alter the wavelength. The increase in frequency is a result of the observer encountering more wavelengths in a given time."
http://a-levelphysicstutor.com/wav-doppler.php
Albert Einstein Institute: "In the above paragraphs, we have only considered moving sources. In fact, a closer look at cases where it is the receiver that is in motion will show that this kind of motion leads to a very similar kind of Doppler effect. Here is an animation of the receiver moving towards the source:
https://www.einstein-online.info/wp-...ein-Online.gif
By observing the two indicator lights, you can see for yourself that, once more, there is a blue-shift - the pulse frequency measured at the receiver is somewhat higher than the frequency with which the pulses are sent out. This time, the DISTANCES BETWEEN SUBSEQUENT PULSES ARE NOT AFFECTED, BUT STILL THERE IS A FREQUENCY SHIFT: As the receiver moves towards each pulse, the time until pulse and receiver meet up is shortened. In this particular animation, which has the receiver moving towards the source at one third the speed of the pulses themselves, four pulses are received in the time it takes the source to emit three pulses."
http://www.einstein-online.info/spotlights/doppler.html
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