A point source of light S, placed at a
distance L in front of the centre of a mirror of width d,
hangs vertically on a wall. A man walks in front of the
mirror along a line parallel to th mirror at a distance
2L form 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) 3 d.

Explanation

(d) the ray diagram will be as shown in fig.
` HI=AB=d`
`DS=CD=(d/2)`
` "Since" AH=2AD`
`:. GH=2 CD=2(d)/(2)=d`
Similarly, `IJ=d`
`:. GJ =GH+HI+IJ=d+d+d=3d`.