Photoelectric Effect

Photoelectric effect:

        Photon:

                 in 1905 Einstein suggest that light(electromagnetic radiations) is made up of tiny particles known as photon.
  • photons are the packets of energy.
  • Einstein suggested that energy is not emitted continuously but is emitted as individual amount of energy known as Quantum energy.

Energy of Photon:

The energy of photon is given by Einstein 
                                   E=hv
where,
               E= energy of photon
               h=plank's constant
               v=frequency

Properties of Photon:

  1. Photon have no mass.
  2. Photon posses no charge and are not deflected by electric or magnetic field.
  3. The values of all quantum number is zero for Photon.
  4. In empty space they move with the speed of light.
  5. when radiations interact with matter it act as photon.
  6. energy and momentum relation is given by    E=pc
  7. Photon are virtual particles 
  8. their energy is directly proportional to frequency and inversely proportional to wavelength.

Photoelectric effect:

It was the key of concept of photon.It states that
          " when light falls on the surface of metal it ejects electron from the surface of metals.
theses ejected electron are called photo electron and phenomena is called photoelectric effect.

Explanation:

Consider a light of suitable frequency falls on the surface of metal it ejects an electron from the surface of metal  

we can say it as the collision between two particles i.e photon and electron.The electron are emitted from the surface of metal with some velocity and as we know that electron has some mass it means that it will posses kinetic energy. The energy of Photo is given by

                                       Ephoton = K.E + Φ
where
                      Φ = work function
work function is the minimum amount of energy required to eject electron from the metal surface.
                              Φ = hν0
where,
                            ν0 =Threshold frequency 
Minimum frequency required to eject photoelectron.

we can calculate the kinetic energy as well
                    K.E = Ephoton - Φ
 According to Einstein
                            
                           Ephoton = hν 
So,
                           K.E = hν - Φ

  Or,
                        1/2mv2  =hν−Φ

 Relation K.E and intensity:

                 Kinetic energy of the electron does not depend upon the intensity of photon but 

more the intensity more the no of photon more is the number of electron ejected.

Relationship between K.E and Frequency.

                   More the frequency more is K.E of the electron ,they have direct relationship.

                    

Location: Pakistan

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