Question

The aperture diameter of a plano convex lens is 4 cm and its thickness at the centre is1mm. If its refractive index is 1.5, its focal length is
1) 20 cm
2) 40 cm
3)10 cm
4)25 cm​

Answer 1

Answer:

it is answer c

Explanation:

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Answer 2

Answer is (2). 40 cm