Photoelectric effect

Definition

The photoelectric effect is the emission of electrons from a material when it is exposed to light. This phenomenon demonstrates that light can act as both a wave and a particle.

5 Must Know Facts For Your Next Test

1. Albert Einstein explained the photoelectric effect in 1905, which contributed to his Nobel Prize in Physics in 1921.
2. The energy of the emitted electrons depends on the frequency of the incident light, not its intensity.
3. There is a threshold frequency below which no electrons are emitted, regardless of light intensity.
4. The photoelectric effect provided key evidence for the quantization of energy and the existence of photons.
5. Einstein's equation for the photoelectric effect is $K_{max} = hf - \phi$, where $K_{max}$ is the maximum kinetic energy of emitted electrons, $h$ is Planck's constant, $f$ is the frequency of incident light, and $\phi$ is the work function of the material.

Review Questions

• What did Einstein's explanation of the photoelectric effect demonstrate about the nature of light?
• Why does increasing the intensity of light not affect the energy of emitted electrons in the photoelectric effect?
• How does the threshold frequency relate to the emission of electrons in different materials?

Related terms

Photon: A quantum particle representing a discrete quantity of light or electromagnetic radiation with energy proportional to its frequency.

Work Function:

The minimum amount of energy required to remove an electron from a solid material.

Planck's Constant: $h$ represents Planck's constant, a fundamental constant equal to approximately $6.626 \times 10^{-34} \text{Js}$, used to describe quantized energy levels.