What does the energy of a photon depend on?

The energy of a photon is primarily determined by its frequency. This relationship is defined by the equation (E = h \cdot f), where (E) is the energy of the photon, (h) is Planck's constant, and (f) is the frequency of the electromagnetic wave. As the frequency increases, the energy of the photon increases, meaning that higher frequency light (such as ultraviolet light) is more energetic than lower frequency light (such as infrared light).

While wavelength is inversely related to frequency—meaning that a photon with a longer wavelength has a lower frequency and thus lower energy—the energy is directly computed from the frequency itself. Therefore, focusing on the frequency gives a more straightforward understanding of how to determine a photon’s energy.

The amplitude of the wave does not affect the energy of individual photons; rather, amplitude relates to the intensity or brightness of the light. Likewise, velocity does not play a role in this particular context as it is constant for light in a vacuum.