A mirror of width 'l' m is kept on a wall. A person is approaching the mirror from the front. An observer is behind a screen has a view of the mirror as shown. How far from the mirror will be person be when the observer will be able to see him in the mirror.

Question

 

$(a)\;l\;m \\ (b)\;\frac{l}{3}\;m \\ (c)\;\frac{l}{2}\;m \\ (d)\;2l \;m $