JEE PHYSICS MCQ: RAY OPTICS

1 Medium

1 of 1

Application +4 | -1

The two surfaces of a biconvex lens has same radii of curvatures. This lens is made of glass of refractive index

\mathrm{1}\mathrm{.5}

and has a focal length

\mathrm{10}\,\,\mathrm{cm}

in air. The lens is cut into two equal halves along a plane perpendicular to its principle axis to yield two plano-convex lenses. The two pieces are glued such that the convex surfaces touch each other. If this combination lens is immersed in water (refractive index

\mathrm{ = 4}\,\mathrm{/}\,\mathrm{3}

), its focal length (in cm) is

View answer and explanation

Correct option: D

Option D (40) is correct because the focal length of the combination lens immersed in water is calculated using the lens maker's formula and refractive indices.

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In refraction, light waves are bent on passing from one medium to the second medium, because, in the second medium A double convex lens is made of glass which has its refractive index 1,45 for violet rays and 1.50 for red rays. If the focal length for violet ray is

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