Question

Parallel beam of light is incident on a concave mirror with radius of curvature $\sqrt { 2 }$ m which is subtending an angle 90° at C. The length on principal axis illuminated by reflected light –

• A. $\left( 1 - \frac { 1 } { \sqrt { 2 } } \right)$m
• B. $\sqrt { 2 } \left( 1 - \frac { 1 } { \sqrt { 2 } } \right)$
• C. $\left( 1 + \frac { 1 } { \sqrt { 2 } } \right)$
• D. None of these

Answer 1

Answer: (A)

$\left( 1 - \frac { 1 } { \sqrt { 2 } } \right)$m

Answer 2

length ilhuminated = x – f = – $\frac { \mathrm { R } } { 2 }$

= $\frac { \mathrm { R } } { \sqrt { 2 } }$ – $\frac { \mathrm { R } } { 2 }$ = $\left( 1 - \frac { 1 } { \sqrt { 2 } } \right)$m