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Light is affected by the change in the speed of the source as the frequency of light changes. This is called the Doppler effect, where the red shift can be observed in galaxies moving away from us.

Was the Doppler effect taken into account when measuring the speed of colored light?

Even with the constant speed of light in a vacuum, the speed of the observer can change the speed of the received light, but what is noticeable is that there is no change in the speed of light regardless of the speed of the observer.

Here this made me wonder if the shift makes us see light differently, doesn't this mean that the Doppler effect on light was neglected when measuring the speed of colored light?

This leads me to a fundamental question: How was the speed of colored light measured in a vacuum?

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    $\begingroup$ "the speed of the observer can change the speed of the received light, ". No, it can't, and it doesn't. The Doppler effect does not change the speed of light. $\endgroup$
    – ProfRob
    Commented Aug 26 at 8:45
  • $\begingroup$ In vacuo the speed of electromagnetic radiation is independent of frequency. Color does not matter. $\endgroup$
    – my2cts
    Commented Aug 26 at 9:03
  • $\begingroup$ What is colored light? $\endgroup$
    – Damian
    Commented Aug 26 at 10:16
  • $\begingroup$ @damian light that is not white: light which has a chromaticity other than white $\endgroup$
    – Harrychink
    Commented Aug 26 at 11:08
  • $\begingroup$ To add to what @ProfRob said: The Doppler effect results from the speed of light being constant. It's already baked into the formalism. $\endgroup$
    – paulina
    Commented Aug 26 at 11:08

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The experiment that I am aware of which places the tightest limits is

Schaefer. Severe Limits on Variations of the Speed of Light with Frequency. phys.rev.lett. 82:4964-4966. 1999.

https://arxiv.org/abs/astro-ph/9810479

In this experiment light of 30 keV and 200 keV were found to have the same speed with an experimental uncertainty of $\Delta c/c=6.3 \ 10^{-21}$.

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