Chapter 44: Problem 1

Question: A concave shaving mirror has radius of curvature of $R=35~{\rm cm}$. It is positioned so that the image of the mans face is |m| = 2.7 times the size of the mans face. How far from the mirror is the mans face?

Solution: We assume that the image is not inverted,

$${1\over O}+{1\over I}~=~{1\over O}-{1\over m O}~=~{1\over O} {m-1\over m}~=~{2\over R}$$

from which we find that $O=11~{\rm cm}$.