A photon is a fundamental particle of light and electromagnetic radiation. It is a quantum of the electromagnetic field and is considered to be the basic unit of all forms of electromagnetic radiation, including visible light. Photons are elementary particles, meaning they are not composed of smaller constituents.
Key characteristics of photons include:
- Zero Rest Mass: Photons have zero rest mass, meaning they do not possess mass when at rest.
- Wave-Particle Duality: Photons exhibit both wave-like and particle-like properties. In certain experiments, they display interference patterns characteristic of waves, while in others, they behave as discrete particles.
- Energy and Frequency: The energy of a photon is directly proportional to its frequency, and inversely proportional to its wavelength, as described by the equation E = hf, where E is energy, h is Planck’s constant, and f is frequency.
- Travel at the Speed of Light: Photons always travel at the speed of light in a vacuum (approximately 3 x 10^8 meters per second).
Photons play a crucial role in the interactions of electromagnetic forces, carrying energy and momentum. They are central to understanding phenomena such as the photoelectric effect, where light striking a material surface can eject electrons. Additionally, photons are integral to the field of quantum mechanics and the understanding of particle-wave duality.