The light radiations with discrete quantities of energy are called photons. Photons are elementary particles that are the quantum of the electromagnetic field, including electromagnetic radiation such as light, and the force carrier for the electromagnetic force. In quantum mechanics, the energy of a photon is quantized, meaning it exists only in discrete amounts. The energy $$E$$ of a photon is given by the equation $$E = hf$$, where $$h$$ is Planck's constant (approximately $$6.626 \times 10^{-34} m^2 kg / s$$) and $$f$$ is the frequency of the electromagnetic wave. This principle supports the particle theory of light, where light can be viewed as consisting of particles or photons, in contrast to the classical wave theory of light.