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## QuestionPhysicsClass 12

Light from a point source in air falls on a spherical glass surface$$(n=1{\cdot}5$$ and radius of curvature $$=20\;\text{cm})$$. The distance of the light source from the glass surface is $$100\;\text{cm}$$. At what position the image is formed?

Given data,
Refractive index of air $$n_1=1$$
Refractive index of glass $$n_2=1.5$$
Radius of curvature $$R=20\;\text{cm}$$
Distance between light source and glass surface $$u=-100\;\text{cm}$$
As object is in rarer medium, so refraction takes place from rarer to denser medium.
We know, for refraction from rarer to denser medium by spherical surface is given by,
$$\frac{n_2} v-\frac{n_1} u=\frac{n_2-n_1} R$$$${\cdots}(i)$$ $$\{$$where $$v$$  is distance of image from glass surface$$\}$$
Putting all values in equation $$(i)$$
$$\frac{1{.}5} v-\frac 1{-100}=\frac{1{.}5-1}{20}$$
$$\Rightarrow v=100\;\text{cm}$$