Question

A point source of light B is placed at a distance 100 cm infront of the centre of a mirror width 30 cm hung vertically on a wall. A man walks infront of the mirror at a distance 2.0 m from it as shown. The greatest distance over which he can see the image of light source in the mirror is –

• A. 15 cm
• B. 30 cm
• C. 60 cm
• D. 90 cm

Answer 1

Answer: (D)

90 cm

Answer 2

In DB'MN ~ DB'AC

$\frac { \mathrm { MN } } { \mathrm { AC } }$ = $\frac { B ^ { \prime } P } { B ^ { \prime } Q }$ , $\frac { 30 \mathrm {~cm} } { \mathrm { AC } }$ = $\frac { 1.0 \mathrm {~m} } { 1 + 2.0 \mathrm {~m} }$

AC = 90 cm