How does the wavelength of light change when a source of light is moving away from an observer, causing a redshift?

Answer

The light waves get stretched out (lengthening).

Light travels in waves, and redshift occurs because these waves are lengthened during transit as the space between the source and the observer expands. Longer wavelengths correspond to redder light.

How does the wavelength of light change when a source of light is moving away from an observer, causing a redshift?

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