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Sahay Sir > Question Answers > JEE Mains Physics 2002-2019 Solved Video Solutions > Chapter 16 - Optics > 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 f1 and f2 respectively. The correct relation between the focal length is

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 f1 and f2 respectively. The correct relation between the focal length is

In figure the number of reflections it makes before emerging form the other end is close to : (refractive index of fiber is 1.31 and sin40^∘=0.64) the optical fiber is l = 2 m long and has a diameter of d=20μm. If a ray of light is incident on one end of the fiber at angle θ1=40^∘