Question

What do you mean by Photoelectric effect ? State and derive Einstein's Photoelectric equation ?

Answer 1

Einsteins photoelectric equation establish the ‘Particle Nature’ of electron. It is based on conservation of energy.

Einstein received Noble prize for photoelectric equation.

Statement—“Total incident energy of light is used into two forms, same part of the energy is used as a work function and remaining part of the energy is used as a kinetic energy of photo electrons."

Mathematically, Einstein equation can be written as,

Incident energy = Work functions + Kinetic energy   ...(1)

Using in eqn (4), (6) and (7)

Eqn. (4), (7), (9), (10) and (11) are called standard form of Einstein's equation. Where,

V = frequency of incident light 

 V₀ = Threshold frequency 

λ = Wavelength of incident light  

 λ₀  = Threshold wavelength

h = plenck's constant

c = speed of light

m = mass of electron

e = charge of an electron

V = stopping potential

V^s = velocity of photo electron

Technical Representation of Einstein's equation—Mathematical form of Einstein's eqn   —

Kinetic energy = Incident energy – work function  ...(1)

eVs = hv - ϕ       ....(2)

Dividing eqn (2) by ‘e’

Hence, by knowing slope of U – V_s group the plenck's constant can be calculated. The graph of Incident frequency and stopping potential is straight line whose intercept is negative.