JEE Main 2024 Physics question
The distance between object and its 3 times magnified virtual image as produced by a convex lens is 20 cm. The focal length of the lens used is cm.
Answer: 15
Solution
v = 3u on the same side, v − u = 20 ⇒ u = 10 cm, v = 30 cm; 1/f = 1/10 − 1/30 ⇒ f = 15 cm.