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M o d e l N o . O S - 8 5 1 5 B
Experiment 2: Prism
Required Equipment from Basic Optics System
Light Source
Rhombus from Ray Optics Kit
Blank white paper
Purpose
The purpose of this experiment is to show how a prism
separates white light into its component colors and to
show that different colors are refracted at different
angles through a prism.
Theory
When a monochromatic light ray crosses from one
medium (such as air) to another (such as acrylic), it is
refracted. According to Snell's Law,
sin θ
n
1
the angle of refraction (θ
refraction of both media (n
refraction for light varies with the frequency of the light, white light that enters the
material (at an angle other than 0°) will separate into its component colors as each fre-
quency is bent a different amount.
The rhombus is made of acrylic which has an index of refraction of 1.497 for light of
wavelength 486 nm in a vacuum (blue light), 1.491 for wavelength 589 nm (yellow),
and 1.489 for wavelength 651 nm (red). In general for visible light, index of refrac-
tion increases with increasing frequency.
Procedure
1.
Place the light source in ray-box mode on a sheet of blank white paper. Turn the
wheel to select a single white ray.
Single white ray
2.
Position the rhombus as shown in Figure 2.2. The acute-angled end of the rhom-
bus is used as a prism in this experiment. Keep the ray near the point of the rhom-
bus for maximum transmission of the light.
®
sin θ
= n
1
2
2
) depends on the angle of incidence (θ
2
and n
), as shown in Figure 2.1. Because the index of
1
2
q
Normal to surface
Figure 2.2
Incident ray
q
1
n
1
n
2
Figure 2.1: Refraction of Light
) and the indices of
1
Color
spectrum
E x p e r im e n t 2 : P r i s m
Normal to surface
Surface
q
2
Refracted ray
(n
> n
)
1
2
9
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