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M o d e l N o . O S - 8 5 1 5 B
Experiment 11: Dispersion
Required Equipment from Basic Optics System
Ray Table
D-shaped Lens
Light Source
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
), the index of refraction of the second medium (n
1
and the angle of refraction (θ
(eq. 11.1)
Incident ray
n
1
n
2
We can assume the index of refraction of air (n
1.0. However, the index of refraction of acrylic (n
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
®
), the angle of incidence (θ
2
):
2
θ
θ
n
sin
=
n
sin
1
1
2
2
q
1
Refracted ray
q
(n
2
1
Figure 11.1
in this experiment) is always equal to
2
) depends on the wavelength, or
1
E x p e r im e n t 1 1 : D is p e r s io n
),
1
acrylic
air
> n
)
2
Light Source
Single
Ray
Figure 11.2
Ray Table
90
90
29
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