CBSE Class 12 Physics 2022 Term 2 Delhi Set 3 Solved Paper

Question : 4

Total: 4

(a) Give an example each of a metal from which photoelectric emission takes place when irradiated by (i) UV light (ii) visible light. 3
(b) The work function of a metal is 4.50‌eV. Find the frequency of light to be used to eject electrons from the metal surface with a maximum kinetic energy of 6.06×10−19J. 3

Solution:

(a) (i) Photoelectric emission takes place when mathrm‌Zn is irradiated with UV radiation.
(ii) Photoelectric emission takes place when mathrm‌Na is irradiated with visible light.(b) Maximum kinetic energy of photoelectron
= Energy of incident photon - Work function
Or, 6.06×10−19=hv−4.5×1.6×1019
Or, hv=13.26×10−19
Or, v=

(13.26×10−19)

(6.6×10−34)

∴v=2×1015Hz

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