What is a photon?

A photon is fundamentally understood as a particle of light. It represents the quantum of electromagnetic radiation, meaning it is the smallest discrete unit of light and all other forms of electromagnetic radiation. Photons possess both wave-like and particle-like properties, a concept encapsulated in quantum mechanics known as wave-particle duality.

When we refer to a photon, we are discussing its role as an energy carrier. Each photon has a specific amount of energy that is directly proportional to its frequency, according to the equation (E = hf), where (E) is energy, (h) is Planck's constant, and (f) is the frequency. This duality allows photons to exhibit characteristics of both waves, such as interference and diffraction, as well as particle attributes, like being counted and having momentum.

Understanding that photons are particles helps to clarify phenomena such as the photoelectric effect, where light behaves as though it consists of particles striking a surface and causing electrons to be emitted. This particle perspective is a cornerstone of modern physics and is essential in various technological applications, from lasers to solar cells.