Question

A ray of light traveling parallel to the principal axis of a concave mirror strikes the mirror at an angle of incidence q. If radius of curvature of the mirror is R, then after reflection, the ray meets the principal axis at a distance x from the centre of curvature. Then x is –

• A. $\frac { \mathrm { R } } { 2 }$
• B. $\frac { \mathrm { R } } { 2 \tan \theta }$
• C.
• D.

Answer 1

Answer: (C)

Answer 2

$\frac { \mathrm { x } } { \sin \theta }$ = $\frac { \mathrm { R } } { \sin ( \pi - 2 \theta ) }$ so x =

= $\frac { \mathrm { R } } { \sin 2 \theta }$