A photon is the quantum of what type of energy?

• A. Thermal energy
• B. Kinetic energy
• C. Potential energy
• D. Electromagnetic energy

Answer: (D)

A photon is the quantum of electromagnetic energy. Light and other forms of electromagnetic radiation come from oscillating electric and magnetic fields, and that energy is quantized into discrete packets called photons. Each photon carries energy proportional to its frequency, E = h f (or E = hc/λ), which means light is made of individual quanta of EM energy rather than a continuous, freely changing amount. This is distinct from thermal energy, which arises from the random motion of many particles; from kinetic energy, which is the energy of motion of a body; and from potential energy, which is energy stored by position in a field. A photon is not simply one of those forms of energy; it is the smallest unit of energy associated with the electromagnetic field itself, enabling processes like absorption and emission that transfer EM energy between light and matter.