Question

A person wishes to use a plane mirror on a wall to view both his head and his feet as he stands in front of the mirror, the required length of the mirror:

• A. Is equal to the height of the man
• B. Is equal to one half of the height of the man
• C. Depends on the distance from the man to the mirror
• D. Depends on both the height of the man and the distance from the man to the mirror

Answer 1

The correct option is B Is equal to one half of the height of the man

The figure shows a man of height $H$. $h_1$ is the height of head top from eye and $h_2$ is the height of eye from his feet.

Now, from the figure which is self explanatory,

the length of mirror, $H^{{}^{\prime }}=\frac{h_1}{2}+\frac{h_2}{2}$

$⟹H^{{}^{\prime }}=\frac{h_1+h_2}{2}=\frac{H}{2}$

Length of mirror should be at least half of the height of man, and from figure it is also clear how that mirror should be kept.

Answer-(B)