®
M o d e l N o . O S - 8 5 1 5 B
E x p e r i m e n t 1 1 : D i s p e r s i o n
29
Experiment 11: Dispersion
Purpose
The purpose of this experiment is to determine the index of refraction of acrylic at
two different wavelengths.
Theory
When light crosses the boundary between two transparent media, it is refracted.
Snell’s Law expresses the relationship between index of refraction of the first medium
(
n
1
), the index of refraction of the second medium (
n
2
), the angle of incidence (
θ
1
),
and the angle of refraction (
θ
2
):
(eq. 11.1)
Figure 11.1
We can assume the index of refraction of air (
n
2
in this experiment) is always equal to
1.0. However, the index of refraction of acrylic (
n
1
) depends on the wavelength, or
color, of the light. Therefore, the different wavelengths present in an incident ray of
white light will be refracted at different angles. The wavelength dependence of a
material’s index of refraction is known as dispersion.
Setup
1.
Place the light source in ray-box mode on a
flat tabletop. Turn the wheel to select a single
ray.
2.
Put the ray table in front of the light source so
the ray from the light source crosses the exact
center of the ray table (see Figure 11.2).
3.
Put the acrylic D-shaped lens on the ray table
in the marked outline. Turn the ray table so
Required Equipment from Basic Optics System
Ray Table
D-shaped Lens
Light Source
n
1
θ
1
sin
n
2
θ
2
sin
=
Refracted ray
(
n
1
>
n
2
)
Incident ray
n
1
n
2
q
1
q
2
acrylic
air
90 90
80
70
60
50
60
70
80
20
30
40
10
0
10
40
30
20
70
60
50
80
90
80
50
60
70
20
30
40
10
0
10
40
30
20
50
COMPONENT
COMPONENT
NORMAL
NORMAL
BASIC OPTICS
RAY
TABLE
OS-8465
RA
90 90
80
70
60
50
60
70
80
20
30
40
10
0
10
40
30
20
70
60
50
80
90
80
50
60
70
20
30
40
10
0
10
40
30
20
50
COMPONENT
COMPONENT
NORMAL
NORMAL
BASIC OPTICS
RAY
TABLE
OS-8465
RA
Light Source
Ray Table
Single
Ray
Figure 11.2
Summary of Contents for OS-8515B
Page 6: ... Basic Optics System About the Experiments 6 ...
Page 26: ... Basic Optics System Experiment 9 Apparent Depth 26 ...
Page 38: ... Basic Optics System Experiment 13 Telescope 38 ...
Page 42: ... Basic Optics System Experiment 14 Microscope 42 ...
Page 44: ... Basic Optics System Experiment 15 Shadows 44 ...
Page 46: ... Basic Optics System Telescope and Microscope Test Pattern 46 ...