What is a photon?

A photon is defined as a particle of light energy. This concept emerges from the field of quantum physics, where light can exhibit both wave-like and particle-like properties, a phenomenon known as wave-particle duality. When considering light, it is composed of discrete packets of energy called photons. Each photon carries a specific amount of energy that is directly proportional to its frequency, which is a fundamental aspect of how light interacts with matter.

Photons do not have mass, and they travel at the speed of light in a vacuum, which is approximately 3 x 10^8 meters per second. This particle-like behavior accounts for various phenomena, such as the photoelectric effect, where light can eject electrons from materials, demonstrating that light can indeed be treated as a collection of photons.

Understanding this definition helps to clarify the properties of light and its interactions in different physical situations, making the notion of a photon fundamental in both physics and technology, such as in lasers and solar cells.