Chapter 15:
Mirrors and Lenses
Practice Test
1.
A light ray strikes a plane mirror. The angle between the incident light ray and the normal to the mirror is 55°. What is the angle between the reflected ray and the normal?
a.
35°
b.
90°
c.
55°
d.
20°
Hint
2.
The magnification of a mirror or lens equals the image size divided by the object size. If a plant cell with a diameter of 0.0035 mm is magnified so that the diameter of the image is 0.028 cm, what is the magnification?
a.
12.5
b.
80
c.
800
d.
8
Hint
3.
A light source is placed a distance of 1.2 m from a concave mirror on the optical axis. The reflected light rays are parallel and form a light beam. What is the focal length of the mirror?
a.
2.4 m
b.
1.2 m
c.
1.0 m
d.
0.6 m
Hint
4.
In some types of reflecting telescopes the eyepiece is located behind the concave mirror. A small curved mirror in front of the concave mirror reflects light through a hole in the concave mirror to the eyepiece. Suppose a circular concave mirror with a diameter of 50 cm has a hole with a diameter of 10 cm. What is the ratio of the reflecting area of the mirror with the 10-cm hole to the reflecting area of the same mirror without the hole?
a.
1.04
b.
0.20
c.
0.80
d.
0.96
Hint
5.
The magnification equals the image size divided by the object size. The magnification also equals the distance of the image from the lens divided by the distance of the object from the lens. A penny has a diameter of 2.0 cm. The image formed by a convex lens has a diameter of 5.2 cm and is 6.0 cm from the lens. What is the distance between the penny and the lens?
a.
15.6 cm
b.
3.2 cm
c.
2.3 cm
d.
2.8 cm
Hint
6.
A small insect is being viewed in a compound microscope. The objective lens of the microscope forms a real image 20 times larger than the insect. The eyepiece lens then magnifies this real image by 10 times. What is the magnification of the microscope?
a.
20
b.
200
c.
10
d.
2
Hint
7.
A convex lens in a magnifying glass has a focal length of 5 cm. How far should the lens be from an object if the image formed is virtual, enlarged, and upright?
a.
less than 5 cm
b.
greater than 10 cm
c.
5 cm
d.
between 5 cm and 10 cm
Hint
8.
A concave mirror forms a real image that is 3/4 the size of the object. How far is the object from the mirror?
a.
less than one focal length from the mirror
b.
at the focal point of the mirror
c.
3/4 of the focal length from the mirror
d.
more than one focal length from the mirror
Hint
9.
Astronomers have proposed building the OWL telescope (OverWhelmingly Large telescope) with a mirror 100 m in diameter. The diameter of the Hubble Space Telescope mirror is 2.4 m. What percentage of the surface area of the OWL mirror would be covered by the surface area of the Hubble mirror?
a.
41.7%
b.
97.6%
c.
0.058%
d.
2.4%
Hint
10.
Light enters your eye through the pupil. In the dark, the pupil is dilated and has a diameter of about 1 cm. The Keck telescope has a mirror with a diameter of 10 m. If both the pupil and the Keck mirror are circles in shape, what is the ratio of the area of the Keck telescope mirror to the area of a dilated human pupil?
a.
1,000,000
b.
10,000
c.
10
d.
1,000
Hint
