• Other Laws|Blog|
• By Taxmann
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• Last Updated on 22 September, 2022

1. A Quick Review

2. Einstein Photoelectric Relation

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## 1. A Quick Review

• Energy of photon of frequency (n) or wavelength (l)

E = hv =  (eV – A)

• Momentum of photon P =
• Effective mass of photon

Note: Net mass of photon is zero

• Intensity of light =

(1) Surface is perfectly reflecting

(2) Surface is perfectly absorbing

• The phenomenon of ejection of electron due to absorption of photon of suitable frequency is known as photo electric effect.
• The minimum energy of photon require to just eject electron from metal surface is known as work function of metal.
• The frequency of photon corresponding to work function of metal is known as threshold frequency.

• v threshold =
• The wavelength of photon corresponding to work function of metal is known as threshold wavelength.
• y threshold =
• In photoelectric effect one photon interact with only one electron.

## 2. Einstein Photoelectric Relation

• Kinetic energy of ejected electron = Energy of photon – work function.

• If we increase the frequency (or decrease the wavelength) of photon. The energy of photon will increase and hence energy of ejected electron will increase.
• If we increase intensity of photon (i.e. No. of photon falling on unit area in unit time) then No. of ejected electron will increase and hence photo current will increase.
• The magnitude of minimum potential to just stop the flow of photo current is known as cut-off potential. It depend on frequency or wavelength of incident photon.

• If we increase the intensity of photon, saturation current will increase but cut-off potential (stopping potential) will remain same.

• If we increase the frequency (decrease the wavelength of photon, cut-off potential (stopping potential) will increase but saturation current will remain same.
• De-Broglie hypothesis of matter wave states that wave nature can also be associated with microscopic particle.
• Wavelength of matter wave
• For Charged particle (E) = qV
• For non-relativistic motion P =

So,

Where,

h = plank constant
m = mass of particle
E = Kinetic energy of particle
q=charge on particle
V=potential difference across which charged particle is moved

• For electron moved across V-volt potential
• Davisson Germer experiment show wave particle duality.

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## Author: Taxmann

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