In the quantum description of light, which term refers to the energy-carrying particle?

• A. Photons
• B. Electrons
• C. Protons
• D. Neutrinos

Answer: (A)

Light in quantum terms is described as consisting of individual energy packets known as photons. A photon is the energy-carrying particle of light; its energy depends on frequency via E = hν, and it also carries momentum. This quantized view explains how light interacts with matter in discrete steps, such as emission or absorption of specific amounts of energy by atoms. The other options are different particles with distinct roles—electrons, protons, and neutrinos are matter particles with mass and are not the quanta that carry light’s energy. Photons are the massless carriers that mediate electromagnetic radiation, so they are the correct term.