1. Tardigrade
  2. Question
  3. Physics
  4. Monochromatic light frequency f1 incident on a photocell and the stopping potential is found to be V1. What is the new stopping potential of the-cell, if it is radiated by monochromatic light of frequency f2 ?

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Q. Monochromatic light frequency $f_1$ incident on a photocell and the stopping potential is found to be $ V_1$. What is the new stopping potential of the-cell, if it is radiated by monochromatic light of frequency $ f_2 $ ?

Gujarat CETGujarat CET 2006Dual Nature of Radiation and Matter

Solution:

Einstein's photoelectric equation can be written as
$ hf = k + \phi $
but k = $ eV_s, \, V_s$, being stopping potential
$ \therefore hf = e V_s + \phi $ ... (i)
So, $ hf_1 = eV_1 + \phi $ ... (ii)
and $ hf_2 = eV_2 + \phi $ ... (iii)
Subtracting Eq. (ii) from Eq. (iii), we get
$ h ( f_1 - f_2 ) = e (V_1 - V_2 ) $
or $ eV_2 = eV_1 - h ( f_1 - f_2 ) $
or $ V_2 = V_1 + \frac{ h }{ e } ( f_2 - f_1 ) $