Einstein’s Equation

Einstein proposed that light waves consist of packets of energyEnergy is the ability to do work. Energy exists in several forms such as heat, kinetic or mechanical energy, light, potential energy, and electrical energy. Units of Energy: The SI unit... More called quanta or photons and each photon has an energy, hf, h is Plank’s constant (6.6 x 10^-34Js) and f is the frequency of the light i.e E = hf = \( \frac{hc}{\lambda} \)

The incident light must produce enough energy for electrons to overcome the electrostatic force of the metal. The workdone by an incident light to remove electrons from a metal is called work function (w)

Work function is the maximum energy needed to liberate an electron from a metal surface.

Using Einstein relation

W₀ = Work function

hf = W₀ + \( \frac{1}{2} \scriptsize mv^2\)

hf = hf₀ + \( \frac{1}{2} \scriptsize mv^2\)

mv² = hf – W₀

∴hf = hf₀ + E

E = \( \frac{1}{2} \scriptsize mv^2\) – Kinetic energy of the photoelectrons.

E = hf – hf₀

This is known as Einstein’s photoelectric equation.

E = \( \frac{1}{2} \scriptsize mv^2\)= eV

\( \frac{1}{2} \scriptsize mv^2\) = eV

eV is electron volt.

∴ E = eV = hf – hf₀