Optics Question 107

Question: A point object is moving on the principal axis of a concave mirror of focal length $ 24cm $ towards the mirror. When it is at a distance of $ 60cm $ from the mirror, its velocity is $ 9cm/sec. $ What is the velocity of the image at that instant

[MP PMT 1997]

Options:

A) $ 5cm/sec $ towards the mirror

B) $ 4cm/sec $ towards the mirror

C) $ 4cm/sec $ away from the mirror

D) $ 9cm/\sec $ away from the mirror

Show Answer

Answer:

Correct Answer: C

Solution:

$ v _{i}=-{{( \frac{f}{f-u} )}^{2}}.v _{o} $

$ =-{{( \frac{-24}{-24-(-60)} )}^{2}}\times 9 $ = 4 cm/sec.



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