A thin convex lens made from crown glass μ = 3 2 has focal length f ⁡ . When it is measured in two different liquids having refractive indices 4 3 and 5 3 , it has the focal lengths f ⁡ 1 and f ⁡ 2 respectively. The correct relation between the focal lengths is :

Question

A thin convex lens made from crown glass μ = 3 2 has focal length f ⁡ . When it is measured in two different liquids having refractive indices 4 3 and 5 3 , it has the focal lengths f ⁡ 1 and f ⁡ 2 respectively. The correct relation between the focal lengths is :, f ⁡ 1 = f ⁡ 2 f ⁡, f ⁡ 1 > f ⁡ and f ⁡ 2 becomes negative, f ⁡ 2 > f ⁡ and f ⁡ 1 becomes negative, f ⁡ 1 and f ⁡ 2 both become negative

MARKS App · Accepted Answer

Let [ 1 R 1 - 1 R 2 ] = x ∴ 1 f = [ 3 2 1 - 1 ] [ 1 R 1 - 1 R 2 ] ⇒ f = 2 x When in liquid 1 1 f 1 = [ 3 2 4 3 - 1 ] [ 1 R 1 - 1 R 2 ] ⇒ f 1 = 8 x When in liquid 2 1 f 2 = [ 3 2 5 3 - 1 ] [ 1 R 1 - 1 R 2 ] ⇒ f 2 = - 10 x

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