In the photoelectric effect, electrons are emitted from a material (usually a metal) when it is exposed to light. The relationship between the energy of light and the emission of electrons is fundamental and can be explained as follows:
- Photon energy: Light behaves as particles called photons, each carrying energy proportional to its frequency: higher frequency → higher photon energy.
- Work function: Every material has a threshold energy (called the work function) that an electron must overcome to escape from the surface.
- Emission condition: For electrons to be emitted, the photon’s energy must be equal to or greater than the work function.
- Kinetic energy of emitted electrons: The faster the electrons are emitted, the more energetic the incoming photons are above the threshold.
Key insight: The emission of electrons depends on the frequency (energy) of light, not its intensity. Bright light of low frequency cannot emit electrons, while even weak light of high frequency can.