Question

What are photons ? State their properties.
OrWhat is photon ? Prove that its rest mass is zero.

Answer 1

Photons are small quantized energy packets for propogation of light energy as proposed by Max Plank
According to the Relativistic Lorentz transformation formula,

m(at velocity) = rest mass / √ 1-(v/c)^2

Here the velocity of the photon has to be c

Thus ,
rest mass = mass( at velocity) *√ 1-(c/c)^2
= m(at v) * 0
= 0

hence the rest mass of a photon at all instants is zero