Doppler Effect for Light

When a source of light waves is moving toward or away from us, there is also a Doppler effect. If the source is moving toward us, the wavelengths we see are shortened. This means that the color of the light is shifted toward the blue. If the source is moving away, the wavelengths are stretched out, become longer, and the color shifts toward the red. When the speed of the source is considerably less than the speed of light, Equations 1 and 2 correctly give the observed wavelength λ and period T in terms of the source’s wavelength λ₀ and period and T₀ .

.........(1)

.............(2)