Question

A point source of light $B$ is placed at a distance $L$ in front of the center of a mirror of width $d$ hung vertically on a wall. A man walks in front of the mirror along a line parallel to the mirror at a distance $2L$ from it as shown. The greatest distance over which he can see the image of the light source in the mirror is

• A. $d/2$
• B. $d$
• C. $2d$
• D. $3d$

Answer 1

The correct option is D $3d$

According to the following ray diagram
$HI=AB=d$

and
$DS=CD=\frac{d}{2}$
$\therefore AH=2AD\Rightarrow GH=2CD=\frac{2d}{2}=d$
Similarly $IJ=d$ so $GJ=GH+HI+IJ$
$=d+d+d=3d$