Calculate the minimum height of plane mirror required for a person to see full height?
Consider a person AB, such that A represents the highest point on head, B, the lowest point on foot and E is the fixed eye level. The person will be able to see every part of his body if he can see points A and B. Let MN be the minimum length of mirror fixed on the wall, such that rays AM and BN, after reflection, reach the eye of person, thereby forming image A1B1, when produced backward.
In δ AEA1, CM is parallel to AE and C is the mid–point of AA1.
Thus in order to see full length of a person, requires a plane mirror, which is half of its own height. This relation is true for any distance of object from plane mirror.
Here, it must be pointed out that a person can see full length of his body, by turning his head or eyes even in a small mirror. However, the case discussed is for the fixed level of eyes.