Explain how does (i) photoelectric current and (ii) kinetic energy of the photoelectrons emitted in a photocell vary if the frequency of incident radiation is doubled, but keeping the intensity same? Show the graphical variation in the above two cases. 


(i)  Photoelectric current is measured by the number of electrons emitted per second by the metal surface .

  • This is entirely dependant on the number of photons that strike the metal surface with frequency above or equal to the threshold frequency.
  • It is independent of frequency of the incident photons.

graphical variation-01.jpg


(ii)  The variation of kinetic energy with frequency is governed by the Einstein’s Equation for photoelectric effect .

Einstein Equation's for photoelectric effect-01.jpg

Here, KE=hv-hv o

Clearly, Kinetic Energy is linearly dependent on frequency .

Variation of Kinetic Energy wrt Frequency-01.jpg

Hence, the Kinetic energy of photoelectrons emitted would increase with increase in frequency .


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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.