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3. Above threshold frequency the maximum kinetic energy of photo electrons depends upon the frequency of incident light.
4. The photoelectric emission is an instantaneous process.
Einstein’ s Photoelectric Equation
The maximum kinetic energy of photoelectrons
( E k) max = hv – φ = h( v – v o) where v is frequency of incident light and v o is threshold frequency.
Stopping Potential
The minimum negative potential given to anode plate at which photoelectric current becomes zero is called stopping potential( V o).
Maximum kinetic energy of photo electrons( E k) max = 1 / 2 mv 2 max = eV o
Compton Effect
When a monochromatic beam of X – falls on a target containing free electrons. it is scattered. As a result, the electrons recoil and scattered radiation has wavelength longer than incident one. This effect is called Compton effect.
( i) λ’ – λ = λ = Compton shift Δλ = h / m o c( 1 – cos φ) where m o is rest mass of an electron and c is the speed of light h / m o c Compton shift Δλ is maximum, when φ = 180 °