question_answer

A conversing beam of rays is incident on a diverging lens. Having passed though the lens the rays intersect at a point 15 cm from the lens on the opposite side. If the lens is removed the point where the rays meets will move 5 cm closer to the lens. The focal length of the lens is [AIPMT (M) 2011]

A)  - 10 cm

B)       20 cm

C)  - 30 cm

D)       5 cm

Correct Answer: C

Solution :

           

Given,