All about Dual Nature of Radiation and Matter | Physics

Table of Contents

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 =
  • Radiation force

(1) Surface is perfectly reflecting

F_radiation =

(2) Surface is perfectly absorbing

F_radiation =

• • 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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