question_answer

An object is at a distance of 20 m from a convex lens of focal length 0.3 m. The lens forms an image of the object. If the object moves away from the lens at a speed of 5 m/s, the speed and direction of the image will be- [JEE Main 11-Jan-2019 Morning]

A) \[2.26\times {{10}^{-3}}m/s\] away from the lens

B) \[3.22\times {{10}^{-3}}m/s\] towards the lens

C) \[1.16\times {{10}^{-3}}m/s\] towards the lens

D) \[0.92\times {{10}^{-3}}m/s\] away from the lens

Correct Answer: C

Solution :

[c] From the lens equation,                                .(1)

Differentiating eqn. (i),