31.16 - Interactive checkpoint: mirror equations
A frog sits in front of a convex
spherical mirror. The mirror produces
an image of the frog with a lateral
magnification of 1/4. The mirror’s
radius of curvature is 0.260 m. How
far away is the frog from the mirror?
Answer:do = m
31.17 - Interactive problem: optical bench with a mirror
The simulations here challenge you to use the mirror equations. In the first, you are
asked to create an image 13.7 cm from the mirror’s surface as shown in the
illustration and in the simulation. The object is 11.2 cm from the mirror.
You set the focal length of the mirror by dragging the focal point F, or by setting its
value in the control panel. As you change the focal length, you will also be changing
the curvature of the mirror. Once you believe you have set the focal length correctly,
press the CHECK button to test your answer. Be careful with signs!
Your mission in the second simulation to the right is to create a mirror that will have
a magnification of +0.470 for the same object at the same position. Again, you
control the focal length, and to test your answer, press the CHECK button in this
simulation. As a hint: First, determine where the image must be using one formula,
then use another formula to determine the required focal length.
If you have trouble with either of these tasks, review the prior section on the mirror
equations.31.18 - Gotchas
Virtual images do not exist. This may be a philosophical question. They do exist in our minds. They cannot be touched, or projected onto a
piece of paper. In contrast, real images can be projected onto a screen or a piece of paper.
A convex and a concave mirror have the same radius of curvature.This means their focal lengths are identical. The magnitudes of their focal
lengths are the same, but the signs differ. The focal length is positive for a concave mirror and negative for a convex mirror.
A virtual image has a negative image distance. Yes. Conversely, real images have positive image distances.(^590) Copyright 2007 Kinetic Books Co. Chapter 31