Question

A convex meniscus lens is made from glass with refractive index n = 1.52. If the radius of curvature of the convex surface is 20 cm and that of the concave surface is 40 cm, then find out the focal length.

Answer 1

Answer:

given, for convex part, radius of curvature, R1=20 cm  

and for concave part, R2=-40 cm  

and refractive index, µ=1.52

1/f = (n - 1) (1 / R1 + 1 / R2)

1/f = (1.52 - 1) (1 / 20 - 1 / 40)

1/f = 0.52 x (1 / 40)

f = 76.92cm

Explanation:

Answer 2

Answer:

76.92 cm

Explanation:

given, for convex part, radius of curvature, R1=20 cm  

and for concave part, R2=-40 cm  

and refractive index, µ=1.52

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