NDA 2026 Physics question
A biconvex lens is made of a material of refractive index 2 such that the ratio of the radii of curvature of its two faces is 1 : 2. A point source in air is placed on the principal axis of this lens at a distance u from the lens. Which one of the following is correct if the image is formed exactly at the same distance as that of the point source ? (where R is the radius of curvature of the first face)
Answer: (D)
Solution
By the lens maker's formula, , so $f =
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