CUET · PHYSICS · PYQ PAPER 2023

An object approaches a convex lens from distance with a uniform speed of 3 m/s and stops at the focus. The image

A moves away from the lens with an uniform speed of 3 m/s.
B moves away from the lens with an uniform acceleration.
C moves away from the lens with a non uniform acceleration.
D moves towards the lens with non uniform acceleration.

Verified Solution

Answer & Solution

Correct Answer

(C) moves away from the lens with a non uniform acceleration.

Step-by-step Solution

Detailed explanation

\( \frac{1}{v} - \frac{1}{u} = \frac{1}{f} \) \( -\frac{1}{v^2}\frac{dv}{dt} + \frac{1}{u^2}\frac{du}{dt} = 0 \) \( v_i = \frac{dv}{dt} = \left(\frac{v}{u}\right)^2 \frac{du}{dt} \) \( v = \frac{uf}{u+f} \implies v_i = \left(\frac{f}{u+f}\right)^2 (3) \) As object moves from…

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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