Light, when treated as a particle, is called a photon. In modern physics, a photon is defined as:

  • The quantum (smallest packet) of electromagnetic radiation, including visible light.
  • A massless particle that always travels at the speed of light in a vacuum.
  • A carrier of energy that depends on its frequency or wavelength (e.g., blue light photons have more energy than red light photons).

So if someone asks, “What do we call light as a particle?” the precise answer is: we call it a photon.