18
Mirrors and Lenses
1. A student views an image of a vase in a plane
mirror. The apparent height of the vase’s
image is 32 cm and the image appears 45 cm
behind the mirror. How tall is the actual vase
and how far in front of the mirror is the vase?
2. A student uses a spherical concave mirror to
focus the sun's rays to start a campfire. The
sunlight comes to a focus 12.6 cm from the
center of the mirror. What is the mirror's
radius of curvature?
3. What is the focal length of a spherical,
concave mirror that has a radius of curvature
of 426 mm?
Copyright © by Glencoe/McGraw-Hill
4. A spotlight has a spherical, concave mirror
acting as a reflector. Its radius of curvature is
2.26 m. Where should a bulb be placed so
that the mirror reflects a straight beam of
parallel rays? Describe the beam that would
be produced by the spotlight if the bulb is
placed closer to the mirror?
8. Most U.S. passenger cars manufactured
in recent years have slightly convex side
mirrors on the right side. Suppose your car
is equipped with a convex mirror that has a
radius of curvature of 7.24 m. How far away
will a following car appear to be if it is
actually 15.5 m away?
9. A convex lens with a focal length of 16.6 cm
is used to form a real image of an object
placed 35.0 cm from the lens. The height of
the object is 4.5 cm. Calculate the size and
distance of the real image that is formed.
10. The lens of a certain movie projector has a
focal length of 22.50 cm. When a frame of
film is in place, it is 23.25 cm from the lens.
At what distance from the lens would you
place a screen in order to receive a focused
image? If the image on the film is 28 mm
high, how tall is the image formed on the
screen?
5. A spherical, concave mirror has a radius of
curvature of 85.6 cm. A candle is placed on
the principal axis 91.0 cm from the center of
the mirror. At what distance from the mirror
will a real image of the candle form?
11. Since 1838, the diameter of dimes minted
in the United States has been standardized
at 17.9 mm. A magnifying lens that has a
125-mm focal length is used to view a dime.
If the dime is placed 52.5 mm from the lens,
what is the size and distance of the virtual
image?
6. A flower is placed in front of a concave,
spherical mirror at a distance of 0.350 m
from the center of the mirror. A real image
of the flower is observed at a distance of
0.288 m from the center of the mirror.
Calculate the focal length of the mirror.
12. The lens of a magnifying loupe forms a
30.0-mm image of a 2.2 mm insect when the
insect is placed 25 mm from the lens. What is
the focal length of this lens?
7. If the flower in problem 6 is 8.7 cm tall, how
tall is the image of the flower?
13. A student views a tree that is 27.5 m tall
through a concave lens that has a focal length
of 70.0 cm. If the tree is 34.0 m away, how
tall is the virtual image of the tree?
Physics: Principles and Problems
Supplemental Problems • Chapter 18 33