The photoelectric effect is a phenomenon where light (or other electromagnetic radiation) strikes a material’s surface and ejects electrons from it. These ejected electrons are called photoelectrons.
Key Points:
- Cause:
- When photons hit the surface, their energy is transferred to electrons.
- If a photon’s energy is greater than or equal to the work function (minimum energy needed to remove an electron from the material), the electron is freed.
- Energy Relation:
- Photon energy depends on its frequency: higher frequency → higher energy.
- Energy of photon: E=hfE = hf (where hh is Planck’s constant, ff is frequency).
- Threshold Frequency:
- Each material has a minimum frequency of light needed to cause emission.
- Below this frequency, no electrons are emitted, regardless of light intensity.
- Applications:
- Photocells in light sensors and solar panels.
- Photoelectron spectroscopy for material analysis.
- Understanding quantum theory—this effect helped establish that light behaves as particles (photons), not just waves.
In short: The photoelectric effect is proof that light has particle-like properties, and it’s a cornerstone of quantum physics.