Light from a point source in air falls on a spherical glass surface (n = 1.5 and radius of curvature = 20 cm ). The distance of the light source from the glass surface is 100 cm. At what position the image is formed ?

Explanation

`n_(1) = 1 , n_(2) = 1.5`
u = - 100 cm , R = +20 cm
(R is + ve for a convex refracting surface)
`As " " (n_(2))/(v)-(n_1)/(u) = (n_(2)-n_(1))/(R)`
`(1.5)/(v) + (1)/(300) = (1.5-1)/(20)=(1)/(40)`
`(3)/(2v)=(1)/(40)-(1)/(100)=(5-2)/(200)=(3)/(200)`
`(1)/(V) = (1)/(100)`
v = 100 cm
Thus the image is formed at a distance of 100 cm from the glass surface in the direction of incident light.