A photon is a fundamental particle of light, which is a type of electromagnetic radiation. Electromagnetic radiation is a form of energy that is transmitted through electric and magnetic fields, and photons are the smallest units of this energy. Photons have no mass and travel at the speed of light. They carry energy and momentum and interact with matter, such as when they are absorbed by atoms and molecules, causing them to become excited or ionized. In essence, photons are the building blocks of electromagnetic radiation and play a crucial role in the transmission, absorption, and interaction of light and other forms of electromagnetic radiation with matter.
