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.
