01 Force and Motion II
02 Pressure
03 Electricity
04 Electromagnetism
05 Electronics
06 Nuclear Physics
07 Quantum Physics

7.3.1 Einstein’s Photoelectric Theory

  1. The behaviour of photoelectrons in the photoelectric effect can be explained by Einsteịn’s photoelectric equation:
    \[
    h f=W+\frac{1}{2} m v_{\max }^2
    \]
    \(h=\) Planck’s constant
    \(f=\) frequency of incident light wave (photon)
    \(W=\) work function
    \(m=\) mass of photoelectrons
    \(v_{\max }=\) maximum velocity of photoelectrons
  2. Assuming that one photon emits one photoelectron, Einstein’s equation is consistent with the principle of conservation of energy:
    \[
    E = W +K_{\max }
    \]
    \(E =\) energy of incident photon
    \(W =\) work function 
    \(K_{\max }  =\) maximum kinetic energy of photoelectron
  3. In the graph in Diagram below, gradient of the graph = Planck’s constant, \(h\).
  4. Thus, the maximum kinetic energy of photoelectron increases linearly with the frequency of the incident photon.