CUET · PHYSICS · PYQ PAPER 2023

When a light of wavelength 150 nm is incident on silver surface a potential of 3.58 V is required to stop the photoelectrons from reaching the collector plate. Find the potential required to stop photoelectrons when a light of wavelength 200 nm is incident on it ?
(Work function of silver is 4.7 eV)

A 1.51 V
B 2 V
C 3 V
D 7.7 V

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Answer & Solution

Correct Answer

(A) 1.51 V

Step-by-step Solution

Detailed explanation

\(E = \frac{hc}{\lambda}\) \(E = \frac{1240 \text{ eV}\cdot\text{nm}}{200 \text{ nm}} = 6.2 \text{ eV}\) \(V_s = E - \phi\) \(V_s = 6.2 \text{ eV} - 4.7 \text{ eV} = 1.5 \text{ V}\)

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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When a light of wavelength 150 nm is incident on silver surface a potential of 3.58 V is required to stop the photoelectrons from reaching the collector plate. Find the potential required to stop photoelectrons when a light of wavelength 200 nm is incident on it ?(Work function of silver is 4.7 eV)

Step-by-step Solution