The change in the wavelength of electromagnetic radiation in a gravitational field predicted by general relativity.
A heuristic Newtonian derivation gives
(1)
where is the shifted wavelength, is the rest wavelength, h is Planck's constant,
c is the speed of light, is the rest energy, E is the shifted energy, m is a fictional "mass" of
photon (which is subsequently canceled out), G is the gravitational constant, and r is the distance from the
gravitating body with mass M.
