A rays coming from an object which is situated at ∞ distance in air and falls on a spherical glass surface (n = 1.5). Then the distance of image will be R is the radius of curvature of a spherical glass.

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(3) 3R. Given: object at infinity in air, so n₁=1; refraction at a single spherical surface into glass of n₂=1.5; radius of curvature R. Idea: for refraction at one spherical surface, (n₂)/v-(n₁)/u=(n₂-n₁)/R. This is not the lens formula — there is only one surface here, not two. Rays from infinity arrive parallel, so u=∞ and the term (n₁)/u vanishes. That leaves (n₂)/v=(n₂-n₁)/R, so v=(n₂R)/(n₂-n₁). Putting in the numbers: v=(1.5R)/(1.5-1)=(1.5R)/(0.5)=3R. The image forms inside the glass, a distance 3R from the surface.

A rays coming from an object which is situated at ∞ distance in air and falls on a spherical glass surface (n = 1.5). Then the distance of image will be _________ R is the radius of curvature of a spherical glass.

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