Physics class 12th Einstein photoelectric equation

Einstein's Photoelectric Equation


Einstein's photoelectric equation explains how light interacts with matter, particularly how light ejects


electrons from a material. It introduced the concept that light behaves as discrete energy quanta
(photons).


Einstein's Photoelectric Equation:
hv = W + K_max


where:
- h = Planck's constant (6.626 x 10^(-34) J·s)
- v = Frequency of the incident light
- W = Work function (minimum energy required to eject an electron)
- K_max = Maximum kinetic energy of the ejected electron


Explanation of Terms:
1. Energy Quantum of Radiation (Photon Energy)
- Light consists of discrete packets of energy called photons.
- The energy of each photon is given by: E = hv.


2. Work Function (W)
- The minimum energy required to free an electron from a material.
- If photon energy is less than W, no electrons are emitted.


3. Kinetic Energy of Ejected Electrons
- If photon energy is greater than W, the excess energy converts to kinetic energy:
K_max = hv - W.


Experimental Observations Explained by Einstein's Equation:
- Threshold Frequency (v_0): Minimum frequency required for emission.
- If hv < W, no electrons are emitted.
- If hv >= W, electrons are ejected.
- Threshold frequency: v_0 = W/h.


- Instantaneous Emission: Electrons are emitted immediately when photons strike the material.