Question: Q. 13. Plot agraph showing the variation of photoelectric current with intensity of light. The work function for the following metals is given : Na:2.75 eV and Mo : 4.175eV. Which of these will not give photoelectron emission from a radiation of wavelength 3300\AA from a laser beam ? What happens if the source of laser beam is brought closer ?

R [Foreign I, II, III 2016]

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Solution:

Ans. (i)

(ii) Energy of a photon,

E=hcλ Joule  =hceλeV =6.63×1034×3×1081.6×1019×3.3×107eV =3.75eV

1/2

Since ϕ0 of Mo is greater than E,

Mo will not give photo emission.

1/2

There will be no effect of bringing source closer in the case of Mo. In case of Na, photo current will increase.

[CBSE Marking Scheme 2016]

Detailed Answer :

(ii) Try yourself similar to Q. 7, SATQ-II



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