Doppler effect and Speed of light

If light from a moving away object, such as a star, would appear red-shifted (and blue in case of approaching object), why don't we conclude that the speed of light is affected from that. Doesn't it mean that since light from a moving away object appear red, then the speed of light with respect to us has reduced (C-V) ?

phinds
Gold Member
No, the FREQUENCY is affected. That's what red/blue shifted means. The speed is unchanged.

Dale
Mentor
2020 Award
The frequency and the speed are related by ##v=f\lambda## where ##\lambda## is the wavelength. With light ##\lambda## changes as the reciprocal of ##f##, so ##v## remains constant.

The frequency and the speed are related by ##v=f\lambda## where ##\lambda## is the wavelength. With light ##\lambda## changes as the reciprocal of ##f##, so ##v## remains constant.

So, this must be true even in case of sound. So, does the speed of sound also remain constant in such case?

Bandersnatch