Light from a point source in the air falls on a convex spherical glass surface having radius of curvature 20 cm and refractive index 1.5. The distance of the light source from the glass surface is 100 cm. The distance of the image from the glass surface is:

100 cm

The correct answer is Option (3) → 100 cm

For refraction at spherical surface:

$\frac{n_2}{v}-\frac{n_1}{u}=\frac{n_2-n_1}{R}$

Given: $n_1=1$, $n_2=1.5$, $u=100$, $R=-20$

$\frac{1.5}{v}-\frac{1}{100}=\frac{0.5}{-20}$

$\frac{1.5}{v}-0.01=-0.025$

$\frac{1.5}{v}=-0.015$

$v=-100$

Distance of the image = 100 cm (on the same side as the object).