An object is placed 30 cm away from a convex lens of focal length 10 cm and a sharp image is formed on a screen. Now, a concave lens is placed in contact with the convex lens. The screen now has to be moved by 45 cm to get a sharp image again. The magnitude of focal length of the concave lens is (in cm)
Text Solution
Verified by ExpertsThe correct answer is:
D
For the first condition, 
then 
For the second condition, when concave lens is placed,
(where, F = focal length of combination)
The magnitude of focal length of concave lens,
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