# Gravitational redshift formul

Gravitational redshift formula

Hi,

I am looking for the formula that describes the gravitational redshift as

frequency2 = function(frequency1, radius1, radius2, gravitating_mass)

What I find on the net is http://www.wolframalpha.com/input/?i=gravitational+redshift+from+r1+to+r2" the redshift factor for radius2 being infinity. I don't see how I easily compute a 2nd frequency from a first and from a delta distance.

Anyone know the formula?

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## Answers and Replies

bcrowell
Staff Emeritus
Science Advisor
Gold Member
The redshifts simply combine multiplicatively. Therefore if you know the redshift at infinity you can find the redshift between r1 and r2 by division.

In extension of my original post, I would actually like to have the time derivative of the frequency as the photon climbs up.

Anyone?