How do you calculate the force between two Photons?

Question

when they are locked in an electromagnetic mass?

Answer 1

Photons have no force between them except a gravitational one due to their masses. The energy of a photon is hf where h is Planck's constant and f is the frequency of the photon. The mass equivalent of this energy is hf/(c^2) where c is the speed of light. Newton's law of gravitation says that the gravitational force between two masses is GMm/(r^r) where G is Newton's gravitational constant, M and m are the two masses and r is the distance between their centres. So putting the mass equivalents of the two photons into this formula gives the force between the two photons, in newtons as F=G(h^h)Ff/((c^c)(r^r)) where F and f are the frequencies of the two photons. This is a very, very small force, and the chance that we'll observe any interaction between two photons any time soon is zilch.