CBSE Class 12 Physics 2017 Delhi Set 2 Paper

Question : 4

Total: 8

SECTION -C

In the study of a photoelectric effect the graph between the stopping potential V and frequency v of the incident radiation on two different metals P and Q is shown below :

(i) Which one of the two metals has higher threshold frequency?
(ii) Determine the work function of the metal which has greater value.
(iii) Find the maximum kinetic energy of electron emitted by light of frequency 8× 1014‌Hz for this metal.

Solution:

Identification of metal which has higher threshold frequency
Determination of the work function of the metal which has greater value
Calculation of maximum kinetic energy (Kmax) of electron emitted by light of frequency 8× 1014‌Hz
(i) Q has higher threshold frequency
(ii) Work function ϕ0=hv0
hv0‌=(6.6×10−34)×‌

5×1014

1.6×10−19

‌eV‌
‌=2‌eV‌
Kmax‌=h(v−v0)
‌=‌

6.6×10−34×3×1014

1.6×10−19

‌eV‌
Kmax‌=0.83‌eV

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