Question

If we want to see our full image then the minimum size of the plane mirror:
A. Should be twice of our height
B. Should be of our height
C. Should be half of our height
D. Depends upon our distance from mirror

Answer 1

Hint
The easy method to solve this problem is to calculate the half the value of the height of a man to find the value of the minimum length of the mirror, and to find the bottom position of the mirror, the half the value of the height of the eyes from the ground has to be calculated.
$\Rightarrow {L_{\min }} = \dfrac{H}{2}$
where ${L_{\min }}$ is the minimum length of the mirror and $H$ is the height of the person.

Complete step by step answer
The minimum length of the mirror should be half the height of the man, this is because, at half the length of the height, the angle of incidence equals the angle of reflection, in the case reflection.
The minimum length of a plane mirror to see the full height of one’s body is,
$\Rightarrow {L_{\min }} = \dfrac{H}{2}$
Where $H$ is the height of the person.
The height of a man should be substituted in the above equation to find the minimum length of the mirror. The height of the eyes of a man from the ground should be submitted in the above equation to find the position of the bottom of the mirror.
$\therefore $ The value of the minimum length of the mirror should be half the length of the height of the man.
Thus, option (C) is correct.

Note
The distance at which the man stands from the mirror will not affect the amount of mirror that any person needs to view their full image. The top edge of the mirror to view the full body should be in a level which lies in between our eyes and our head. And the bottom edge of the mirror should be positioned at the halfway distance between our eyes and our feet.