Q17 of 26 Page 1

State two important properties of photon which are used to write Einstein’s photoelectric equation. Define (i) stopping potential and (ii) threshold frequency, using Einstein’s equation and drawing necessary plot between relevant quantities.

The properties of photon which are used to write Einstein’s photoelectric equation are

(i) The rest mass of the photon is zero.


(ii) The energy of the photon is


(i) Stopping potential: For a particular frequency, the minimum negative potential V˳ for which the photocurrent stops or becomes zero is called the stopping potential.


(ii) Threshold frequency: The minimum frequency required for photo electrons to be emitted from a metal surface is called the threshold frequency.


Graph between stopping potential and threshold frequency is:



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