Question

50. Four lenses are made of glass and the radius of
curvature of each face is given below. Which will
have the greatest focal power,
1) 10 cm convex and 15 cm convex
2) 5 cm convex and 10 cm concave
3) 15 cm convex and plane
4) 20 cm convex 30 cm concave​

Answer 1

Use these formulae

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