- Because si is negative, the image is virtual.
- Virtual images are upright.
- The magnification is:
(The fact that the magnification is positive tells us that the
image is upright, as we said in Question 17.) The height of the
image ishi = |m| × ho = (4 cm)= 2.4 cm- Show how the statements made earlier about plane mirrors can
be derived from the mirror and magnification equations.
Here’s How to Crack It
A plane mirror can be considered a spherical mirror with an infinite radius of
curvature (and an infinite focal length). If f = ∞, then 1/f = 0, and the mirror
equation becomes
The image is as far behind the mirror as the object is in front. Also, since so is
always positive, si is negative, so the image is virtual. The magnification is
and the image is upright and has the same height as the object. The mirror and
magnification equations confirm our description of images formed by plane
mirrors.