question_answer

A point source of light B is placed at a distance L in front of the centre 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                    [IIT-JEE (Screening) 2000]

A)            d/2

B)            d

C)            2d

D)            3d

Correct Answer: D

Solution :

                   According to the following ray diagram  \[HI=AB=d\]                    and \[DS=CD=\frac{d}{2}\]                    \[\because \,AH=2AD\]\[\Rightarrow \,\,GH=2CD=\frac{2d}{2}=d\]            Similarly\[IJ=d\]so \[GJ=GH+HI+IJ\]\[=d+d+d=3d\]