PASCO OS-8500 INTRODUCTORY OPTICS SYSTEM - Manual (Page 19)

012-02744K Introductory Optics System
®
13
EQUIPMENT NEEDED:
-Optics Bench -Light Source
-Ray Table and Base -Component Holder
-Slit Plate -Slit Mask
-Cylindrical Lens.
Introduction
As you have seen, the direction of light propagation changes abruptly when light encounters a
reflective surface. The direction also changes abruptly when light passes across a boundary
between two different media of propagation, such as between air and acrylic, or between glass and
water. In this case, the change of direction is called Refraction.
As for reflection, a simple law characterizes the behavior of a refracted ray of light. According to
the Law of Refraction, also known as Snell’s Law:
n
1
sin
θ
1
= n
2
sin
θ
2
The quantities n
1
and n
2
are constants, called indices of refraction, that depend on the two media
through which the light is passing. The angles
θ
1
and
θ
2
are the angles that the ray of light makes
with the normal to the boundary between the two media (see the inset in Figure 4.1). In this
experiment you will test the validity of this law, and also measure the index of refraction for acrylic.
Procedure
Set up the equipment as shown in Figure 4.1. Adjust the components so a single ray of light
passes directly through the center of the Ray Table Degree Scale. Align the flat surface of the
Cylindrical Lens with the line labeled “Component”. With the lens properly aligned, the radial lines
extending from the center of the Degree Scale will all be perpendicular to the circular surface of
the lens.
Experiment 4: The Law of Refraction
Figure 4.1 Equipment Setup
90 80 70 60
50
40
30
20
10
0
0
10
20
30
40
5 0
60
70
80
90
80 70 60
50
40
30
20
10
10
20
30
4 0
5 0
60
70
80
NORM
AL
NORMAL
CO
M P O N E NT
CO
M P O N EN
T
Angle of
Refraction
Angle of
Incidence
Slit Mask
Slit Plate