Question

prove that rest mass of photon is zero

Answer 1

mass of a photon is due to its momentum.When photon comes to rest velocity becomes zero thus mv=p=0.Hence rest mass of a photon is zero.

Answer 2

Answer:

E=hc/λ  (Photon Energy Equation )

E2=(pc+mc2)2  (Mass-Energy Equivalence with Momentum Equation)

p=h/λ (Momentum of a Photon Equation )

Now from the above equations we know that a mass of a photon is dependent on its momentum. And now in this part of physics the concept of rest mass depends upon the special type of relativity . A rest mass is mass of the particle as seen by the observer with "0" speed. So,  when the photon comes to rest its velocity becomes 0 .

Now we know the formula for momentum

p=m*v

p=m*0

 =0.

thus the rest mass of photon is zero.