posted by Pam on .
If you hold a pocket mirror almost at arm's length from your face,and note how much of your face you can see; to see more of your face, should you hold the mirror closer or farther away , or would you have to get a larger mirror? I tried this, but I could see my face in each situation. I really don't understand the question.
The question is how big a mirror do you need to see all of your face, and does it help to move the mirror nearr or farther away. The answer is the mirror must be half as large as your face, in both length and width dimensions, regardless of where the mirror is held.
To figure out why, remember that the mirror is midway between your head and an equal-height virtual image of your face behind the mirror. The mirror must be large enough so that rays drawn from your eye to the entire virtual image of your head strike reflecting surface.
You need a bigger mirror