What is Doppler effect in light? Write the expression for Doppler shift.

Explanation

The time taken between the arrival of two wavefronts will be longer at the observer than it is at the source. Hence when the source of light moves away from the observer, the wavelength of light from the source increases. This is known as the Doppler Effect (red shift)
`(Delta v)/(v)=(v_("radial"))/(c )`
where, 'c' - velocity of light in vacuum
`v_(r) -` radial speed of source of light
`v_("radial")` is positive when the source is moving away from the observer and is - ve when the source is moving towards the observer.