Question :

Write a short note on Threshold Frequency (v0) and Threshold wavelength (&lemda;).

Subject

Physics

Standard

Class 12

Views

856

Asked By

Valentina

Qayanat
Answer / Solution

Threshold Frequency (v0) :

Minimum frequency of incident photon below which no ejection of photoelectrons from a metal surface can take place is known as threshold frequency for that metal. Its value is constant for a particular metal but may be different for different metals.

If v = Frequency of incident phtoton & v0 = Threshold Frequency then

  • If v < v0 → No ejection of photo electron and therefore no Photo electric effect.
  • If v = v0 → Photo electrons are just ejected from metal surface and in this case kinetic energy of electron is zero.
  • If v > v0 → Photo electrons will come out of the surface along with kinetic energy.

Threshold wavelength (0) :

Maximum wavelength of incident photon above which there will be no photoelectric emission from a metal surface is known as threshold wavelength 

L0 = 0 c 

If L = wavelength of incident photon then

(a) if λ < 0 then photo electric effect will take place and ejected electron will possess kinetic energy.

(b)  if  = 0 then Photo electric effect will just take place and kinetic energy of ejected photo electron will be zero   (c)  if  > 0 there will be no Photo electric effect. 


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