Question

Does light or photon has mass? If no, then how photons have momentum

Answer 1

Since photons (particles of light) have no mass, they must obey E = pc and therefore get all of their energy from their momentum. Now there is an interesting additional effect contained in the general equation. If a particle has no mass (m = 0) and is at rest (p = 0), then the total energy is zero (E = 0).

Answer 2

E=pc

E is the total energy of the particle, p is the momentum of the particle (which is related to its motion), c is the speed of light, and m is the mass of the particle. ... Since photons (particles of light) have no mass, they must obey E = pc and therefore get all of their energy from their momentum.