# Should the Energy of a Photon Be Called Its Kinetic Energy Or Its Internal Energy? - Physics

Short Note

Should the energy of a photon be called its kinetic energy or its internal energy?

#### Solution

Relativistic equation of energy :

E^2 = p^2c^2 + m^2c^4       ....(1)

Here, p2c2 = kinetic energy of photon
m02c4 = internal energy of photon
We know photons have zero rest mass. Therefore, m0 = 0. Substituting the value of m0 = 0 in equation (1), we get : E = pc

Thus, the energy of a photon should be called its kinetic energy.

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#### APPEARS IN

HC Verma Class 11, Class 12 Concepts of Physics Vol. 2
Chapter 20 Photoelectric Effect and Wave-Particle Duality
short Answers | Q 6 | Page 363