Question

A meniscus lens has convex surface of curvature 20 cm and concave surface 30 cm. if the lens is constructed of glass (mew=1.5), the focal length will be

Answer 1

hey mate !! this is your answer

A converging meniscus lens has surfaces whose radii of curvature are 20 cm and 30 cm. The lens is made from crown glass whose index of refraction is 1.5. Find its focal length.

1/f = (n-1)(1/R1 + 1/R2)

1/f = (1.5 - 1)(1/20 - 1/30)

1/f = 0.5 x (1/60) = 1/120

f = 120 cm

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