Photon (noun, “FOH-TAHN”)
This word describes a particle of light. A photon is a unit of light that cannot be broken into smaller pieces. This particle is the tiniest possible packet of electromagnetic radiation.
Light’s motion is often described as a wave. But light also has some properties of a particle. One of those properties is that photons can be counted, like beads on a string.
Photons can have different energies. A photon of visible light, such as light that’s the color blue, has a lower energy than an X-ray photon. Scientists can use beams of high-energy X-ray photons to study the properties of matter and molecules.
In a sentence
Human eyes are sensitive enough to see a single photon.