To look total image of a person, the minimum height of a plane mirror is

A plane mirror only needs to be half your height to show your full image, and this holds at any distance from the mirror. The mirror must extend from the midpoint between your eyes and the top of your head down to the midpoint between your eyes and your feet. Rays from the top of the head and the feet reflect at these two edges and reach the eye, so the mirror's length is exactly half the person's height.

• A: A full-height mirror works, but it is larger than the minimum required.
• C: A quarter-height mirror is too short. The rays from the head and feet cannot both reach the eye.
• D: Twice the height is unnecessary and goes beyond the minimum.

The core concept is the law of reflection and image formation by plane mirrors. The image is virtual, erect, the same size as the object, and as far behind the mirror as the object is in front. This is a standard ray-diagram concept in Class 10 optics and a basic building block for understanding periscopes and mirror placement in room and interior design.

Trap: Many aspirants assume the mirror must be as tall as the person, or that the distance from the mirror changes the minimum height. Neither is true. Only the eye position relative to the head and feet matters.