A point object is placed at the center of a glass sphere of radius 6cm and refractive index 1.5. The distance of virtual image from the surface is

Options

A. 6cm
B. 4cm
C. 12cm
D. 9cm

Answer

a.

Explanation

Here, `u=-6cm, v=?, r=-6cm, mu_(1)=1, mu=1.5`
Using the formula of spherical refracting surface,
`(mu_(2))/(v)-(mu_(1))/(u)=(mu_(2)-mu_(1))/(R)`
We have `(1.5)/(v)-(1)/(-6)=(1.5-1)/(-6)rArrv=-6cm`
Alternative method: The ray coming from the point object fall on the glass-air interface normally and hence pass undeviated. Therefore, is we retrace the path of the refracted ray s backward, the image will be formed at the center only.