Answer
a. A plane mirror can be considered a spherical mirror with an infinite radius and focal length.
b. $d_i=-d_o$
c. +1
d. Yes
Work Step by Step
a. As the radius of a sphere increases, the surface becomes more and more flat and approaches the shape of a plane mirror. In other words, a plane mirror is a spherical mirror with infinite radius r and infinite focal length f.
b. Use the mirror equation, 23–2.
$$\frac{1}{d_o}+\frac{1}{d_i}=\frac{1}{f}=\frac{1}{\infty}=0$$
$$\frac{1}{d_o}=-\frac{1}{d_i}$$
$$d_i=-d_o$$
c. Calculate the magnification.
$$m=-\frac{d_i}{d_o}=-\frac{-d_o}{d_o}=+1$$
d. Yes, these results are consistent with those previously derived for plane mirrors.