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 law of reflection states that when a ray of light is made to fall on a reflective surface, the mirrored ray has its angle of reflection, the incident ray has its angle of reflection, and the reflected ray is normal to the surface at a point of incidence.

Complete answer:
A plane mirror has a reflecting surface that is smooth (planar). The angle of reflection equals the angle of incidence for light rays striking a plane mirror. The angle of incidence is the angle formed by the incident ray and the normal of the surface (an imaginary line perpendicular to the surface).

Since the angle of incidence equals the angle of reflection when the mirror is twice the length of the man's height, the minimum length of the mirror should be half his height.A plane mirror's minimum length to see the maximum height of one's body is,
${L_{\min }} = \dfrac{H}{2}$
where ${L_{\min }}$ is the mirror's minimum length and $H$ is the person's height.

To find the minimum length of the mirror, substitute a man's height into the above equation.To find the location of the bottom of the mirror, enter the height of a man's eyes from the ground into the above equation. The minimum length of the mirror should be half of the man's height.

The gap between the man and the mirror has no bearing on the amount of mirror required to see their whole picture. To see the whole body, the top edge of the mirror should be at a distance that is halfway between our eyes and our head.

Hence, the correct answer is option C.

Note:Plane mirrors are commonly used to see an object's reflection, as we already know. Periscopes and kaleidoscopes, motorcycles, shaving mirrors, dentists' mirrors, torch lights, sun cookers, and security-related applications are all examples of plane mirrors.