The Doppler Shift

- This same effect also applies for moving object emitting light.

- Just as our ears perceive an increase in the wavelength of sound as a drop in pitch, our eyes, perceive an increase in wavelength of light as shift to red. This is what we call a "redshift".

- Similarly a decrease in the wavelength of light is perceived as a shift to the blue - a.k.a a "blueshift".