Question

Does light have mass?

Answer 1

We have to find out whether light has mass. The light is composed of small particles known as photons. So, it is clear that if the photon particles had mass then light would also have. Let us now briefly explain it and hence find the answer.

Complete step by step answer:
Light is composed of photons. And the photon is a massless particle. Theories state that iphoton particles have both energy and momentum but no mass.
Sometimes it is said that the photon particle has mass because a photon has energy, $E = h\nu$ where $E$ is the energy associated, $h$ is Planck's constant and $\nu$ is the frequency of the photon.
Again, we know that, energy $E = m{c^2}$ where $m$ is the mass of the particle and $c$ is the speed of the light. Again, as the photon particle has momentum.
We know, momentum $p = mv$ where $m$ is the mass of the particle and $v$ is the velocity of the particle.
It is actually the relativistic mass which is not considered to be the rest mass we are talking about.
So, it is concluded that light has no mass at all.

Note: It must be noted that the mass which we are talking about is the general mass here. But there is a relativistic mass for photons also. We could then consistently talk about the light having mass independently of whether or not it is contained. If relativistic mass is used for all objects, then mass is conserved and the mass of an object is the sum of the masses of its parts. In the modern view, mass is just that part of the energy of a body which is not kinetic energy. Mass is independent of velocity whereas energy is not.