Photon

Definition

A photon is a quantum of electromagnetic radiation, possessing both particle and wave properties. It has no rest mass and travels at the speed of light in a vacuum.

5 Must Know Facts For Your Next Test

1. A photon's energy is given by $E = hf$, where $h$ is Planck's constant and $f$ is the frequency of the associated electromagnetic wave.
2. The momentum of a photon can be calculated using $p = \frac{E}{c}$, where $E$ is the energy and $c$ is the speed of light.
3. In the photoelectric effect, photons striking a material can eject electrons if their energy exceeds the material's work function.
4. Photons exhibit both wave-like behavior (such as diffraction) and particle-like behavior (such as discrete interactions).
5. Photons are electrically neutral and carry no charge.

Review Questions

• What equation defines the energy of a photon?
• How does a photon interact in the photoelectric effect?
• What property allows photons to have momentum despite having no rest mass?

Related terms

Planck's Constant: A fundamental constant ($h$) with a value approximately equal to $6.626 \times 10^{-34}$ Js, used in quantifying photon energy.

Photoelectric Effect: The phenomenon where electrons are ejected from a material when it absorbs photons with sufficient energy.

Wave-Particle Duality: The concept that particles such as photons exhibit both wave-like and particle-like properties.