Write the formula for the Doppler shift for light.

(N/A) For light,the Doppler shift is defined by the change in frequency or wavelength due to the relative motion between the source and the observer.
If the source is moving with a velocity $v$ relative to the observer (where $v \ll c$),the Doppler shift in frequency $\Delta \nu$ is given by:
$\Delta \nu = \nu \left( \frac{v}{c} \right) \cos \theta$
where:
$\nu$ is the original frequency,
$c$ is the speed of light,
$v$ is the relative velocity,
$\theta$ is the angle between the direction of motion and the line of sight.
Alternatively,the shift in wavelength $\Delta \lambda$ is given by:
$\Delta \lambda = \lambda \left( \frac{v}{c} \right) \cos \theta$