Question

A slab of glass of refractive index 1.5 and thickness 3cm is placed with the faces perpendicular to the principal axes of a concave mirror. If the radius of curvature of the mirror is 10 cm, the distance at which an object must be placed from the mirror so that image coincides with the object is –

• A. 9 cm
• B. 10 cm
• C. 11cm
• D. 12 cm

Answer 1

Answer: (C)

11cm

Answer 2

µ = 1.5 = 3 / 2

Dx = t$\left( 1 - \frac { 1 } { \mu } \right)$ = 3 $\left[ 1 - \frac { 1 } { 3 / 2 } \right]$ = 3 $\left( \frac { 1 } { 3 } \right)$

Dx = 1 cm

object distance = 10 + 1 = 11 cm