Question

What is a photon?

Answer 1

particle representing a quantum of light or other electromagnetic radiation. A photon carries energy proportional to the radiation frequency but has zero rest mass.

A photon is the smallest discrete amount or quantum of electromagnetic radiation. It is the basic unit of all light. Photons are always in motion and, in a vacuum, travel at a constant speed to all observers of 2.998 x 10⁸ m/s. This is commonly referred to as the speed of light, denoted by the letter c.