Gravitational redshift is given by the following approximate equation;(adsbygoogle = window.adsbygoogle || []).push({});

[tex]

\frac{\lambda}{\lambda_o} = 1 - \frac{GM}{r c^2}

[/tex]

From http://scienceworld.wolfram.com/physics/GravitationalRedshift.html

Where [tex] \lambda [/tex] is the shifted wavelength and [tex] \lambda_o [/tex] is the rest wavelength.

r is the distance from the gravitating body with mass M

The photon is being emitted from the surface of M directly away from the centre of M.

As r is increased and M constant, the redshift is increased as I expected. The photon has to climb further which reduces its energy which is expressed as a larger wavelength or lower frequency.

But with r held constant and M increased, I expected the energy loss of the photon to be increased at r. The photon now travels through a stronger gravitational field and should lose more energy than when travelling through a weak gravitational field.

But the equation above tells me that if r is held constant and M increased, then the gravitational redshift is reduced.

Where am I going wrong?

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Gravitational redshift equation

**Physics Forums | Science Articles, Homework Help, Discussion**