Final answer:
The energy of light is carried in discrete units known as photons, which are the smallest indivisible particles of light. Einstein's explanation of the particle nature of light to describe phenomena like the photoelectric effect introduced the concept of quantization into the study of electromagnetic radiation.
Step-by-step explanation:
According to the quantum theory of light, the energy of light is carried in discrete units called photons. A photon is the smallest indivisible particle of light, which carries a quantum of energy that is directly proportional to the frequency of the light. The relationship between the energy (E) of a photon and its frequency (v, Greek nu) is described by the equation E = hv, where h is the Planck constant.
Photoelectric Effect and the Particle Nature of Light
In a landmark paper published in 1905, Albert Einstein proposed the particle nature of light to explain the photoelectric effect, an experiment that could not be accounted for by the classical wave theory of light. His theory suggested that light could be thought of as consisting of particles, or photons, each carrying a discrete quantum of energy. This idea of wave-particle duality implies that light can exhibit properties of both waves and particles, depending on the experiment.
Light can encompass a range of electromagnetic radiation, from radio waves to gamma rays. Atoms and light are both quantized; that is, they can exist only in discrete energy levels. In the case of light, these levels are the photons, each with energy defined by its frequency or wavelength (color). Notably, Einstein's concept of photons was in contrast to the classical view of electromagnetic radiation as a continuous wave.