Question

A point object is kept 60 cm in front of a spherical convex surface (n = 1.5, radius of curvature 40 cm). The image formed is ______.

पर्याय

• real, at a distance 1.8 m from the surface.

• virtual, at a distance 1.8 m from the surface.

• real, at a distance 3.6 m from the surface.

• virtual, at a distance 3.6 m from the surface.

Answer 1

A point object is kept 60 cm in front of a spherical convex surface (n = 1.5, radius of curvature 40 cm). The image formed is virtual, at a distance 3.6 m from the surface.

Explanation:

R = 40 cm, μ₂ = 1.5

Refraction at convex spherical surfaces

`mu_2/v - mu_1/u = (mu_2 - mu_1)/R`

`1.5/v - 1/((-60)) = (1.5 - 1)/40`

`1.5/v = 0.5/40 - 1/60`

`1.5/v = 1/80 - 1/60`

`1.5/v = (3 - 4)/240`

`1.5/v = (-1)/240`

`v = -240 xx 15/10`

= −360 cm

= −3.6 m

(−ve) sign so virtual.