Chapter 14:
Light
Practice Test
1.
A laser is used to measure the distance from Earth to the moon. The laser beam is reflected from a mirror on the moon's surface. If the time needed for the laser light to reach the moon and be reflected back is 2.56 s, and the laser light travels at 300,000 km/s, what is the distance to the moon?
a.
384,000 km
b.
192,000 km/s
c.
117,000 km/s
d.
768,000 km
Hint
2.
In the human eye, there are about 7,000,000 cone cells distributed over an area of 5 cm
2
. If cone cells are evenly distributed over this region, how many cone cells are distributed over an area of 2 cm
2
? Express your answer in scientific notation.
a.
2.8 × 10
7
cone cells
b.
2.8 × 10
6
cone cells
c.
4.2 × 10
6
cone cells
d.
1.75 × 10
7
cone cells
Hint
3.
What will happen to a ray of light leaving water and entering air if it hits the boundary at an angle of 49° to the normal? (The critical angle for water and air is 49°.)
a.
It will exit the water at 49°.
b.
It will totally internally reflect.
c.
It will exit the water at 41°.
d.
It will travel along the surface of the water.
Hint
4.
The index of refraction of a material is the speed of light in a vacuum divided by the speed of light in the material. If the index of refraction of the mineral rock salt is 1.52, and the speed of light in a vacuum is 300,000 km/s, what is the speed of light in rock salt?
a.
197,000 km/s
b.
456,000 km/s
c.
300,000 km/s
d.
152,000 km/s
Hint
5.
When a light beam is reflected from a glass surface, only 4% of the energy carried by the beam is reflected. If a light beam is reflected from one glass surface and then another, what is the ratio of the energy carried by the reflected beam after the second reflection, compared to the energy carried by the beam before the first reflection?
a.
0.06
b.
0.08
c.
0.0016
d.
0.02
Hint
6.
A light ray strikes a plane mirror. The angle between the light ray and the surface of the mirror is 25°. What angle does the reflected ray make with the normal?
a.
130° from the mirror
b.
50° from the normal
c.
65° from the normal
d.
65° from the mirror
Hint
7.
About 8% of men and 0.5% of women have some form of color blindness. The number of men who experience color blindness is how many times larger than the number of women who experience color blindness?
a.
8
b.
4
c.
7.5
d.
16
Hint
8.
A ray of light hits a plane mirror at 60° from the normal. What is the angle between the reflected ray and the surface of the mirror?
a.
30° from the mirror
b.
60° from the mirror
c.
30° from the normal
d.
90° from the normal
Hint
9.
A ray of light hits a plane mirror at 35° from the normal. What angle does the reflected ray make with the normal?
a.
70° from the mirror
b.
35° from the normal
c.
35° from the mirror
d.
70° from the normal
Hint
10.
A light ray is reflected from a plane mirror. If the angle between the incident ray and the reflected ray is 104°, what is the angle of incidence?
a.
38°
b.
208°
c.
104°
d.
52°
Hint
