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Einstein explanation of Photoelectric Effect.

 Einstein Explanation of Photoelectric Effect:

  • According to Einstein, electromagnetic radiation of frequency 𝛎 consist of photons, each of energy h𝛎.
  • When a photon of energy h𝛎 is incident on the surface of material, some of its energy is spent in making the electron free and the rest appears as kinetic energy of electron.
  • The electrons at the surface of the material are most loosely bound and require minimum energy for their liberation.
  • This energy is called the work function 𝛟 of material.
  • The maximum kinetic energy of photoelectrons, ejected from the surface is given by;  K.Eₘₐₓ= h𝛎 - 𝛟 
  • The electrons which are tightly bound are ejected with less kinetic energy.
  • Thus the kinetic energy of electron depends on the fact whether it is on the surface of material or it is deeper inside the material.
  • If  𝛎₀ is the frequency of incident radiation such that the photon energy h𝛎₀ is just sufficient to make the electron free from the material, then the ejected electron has zero kinetic energy. This happens when; h𝛎₀= 𝛟 
  • The frequency 𝛎₀ is threshold or cut off frequency and corresponding wavelength 𝛌₀ is called threshold wavelength.
  • Thus threshold frequency is the measure of work function of the material.
  • In terms of photon frequency 𝛎 and threshold frequency 𝛎₀ , Einstein Photoelectric equation can be written as        K.Eₘₐₓ= h𝛎 - h𝛎₀ => K.Eₘₐₓ= h(𝛎 - 𝛎₀) 
  • If V₀ is the stopping potential corresponding to incident radiation then; K.Eₘₐₓ= h(𝛎 - 𝛎₀) = eV₀  

Work function

The minimum energy (𝛟) required to eject an electron from a particular metal surface, is called work function of that metal.

Questions;

Q1) What is the relation between maximum kinetic energy and work function?
Ans)The maximum kinetic energy of photoelectrons, ejected from the surface is given by;  K.Eₘₐₓ= h𝛎 - 𝛟 . Where 𝛟 is work function.
Q2) What is work function?
Ans)The minimum energy (𝛟) required to eject an electron from a particular metal surface, is called work function of that metal.
Q3) Work function is denoted by which symbol?
Ans) 𝛟(phi).
Q4) Fill in the blanks
1)The electrons at the surface of the material are most loosely bound and require ------------ energy for their liberation.
2)The electrons which are tightly bound are ejected with --------- kinetic energy.
3)Thus the ---------- of electron depends on the fact whether it is on the surface of material or it is deeper inside the material.
4)In terms of photon frequency 𝛎 and threshold frequency 𝛎₀ , Einstein Photoelectric equation can be written as ----.
5)The minimum energy (𝛟) required to eject an electron from a particular metal surface, is called ---------- of that metal.
6)When a photon of energy h𝛎 is incident on the surface of material, some of its energy is spent in making the electron ------and the rest appears as --------- of electron.
Ans) 1)The electrons at the surface of the material are most loosely bound and require minimum energy for their liberation.
2)The electrons which are tightly bound are ejected with less kinetic energy.
3)Thus the kinetic energy of electron depends on the fact whether it is on the surface of material or it is deeper inside the material.
4)In terms of photon frequency 𝛎 and threshold frequency 𝛎₀ , Einstein Photoelectric equation can be written as        K.Eₘₐₓ= h𝛎 - h𝛎₀ => K.Eₘₐₓ= h(𝛎 - 𝛎₀) .
5)The minimum energy (𝛟) required to eject an electron from a particular metal surface, is called work function of that metal.
6)When a photon of energy h𝛎 is incident on the surface of material, some of its energy is spent in making the electron free and the rest appears as kinetic energy of electron.

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