PASCO OS-8536 OPTICS TABLE - Manual (Page 13)

9
012-06557A Optics Table
Figure 4.3
Mirror
R
f
Focal Point
The place where the five reflected rays cross each other is the focal
point of the mirror. Measure the focal length from the center of the
concave mirror surface to the focal point. Use the compass to draw a
circle that matches the curvature of the mirror. Measure the radius of
curvature using a rule and compare it to the focal length.
Repeat the procedure for the convex surface of the mirror. Note that
the reflected rays are diverging for a convex mirror and they will not
cross. After you trace the outline of the mirror and the incident and
reflected rays, use a rule to extend the reflected rays back behind the
mirror’s surface.
Experiment 5: Snell’s Law
EQUIPMENT NEEDED
– Light Source – Optics Bench
– Ray Table and Base – Rhombus
– protractor – pencil
Purpose
To use Snell’s Law to determine the index of refraction of the
Acrylic rhombus.
Theory
Snell’s Law states
n
1
sin
θ
1
= n
2
sin
θ
2
where
θ
1
is the angle of incidence,
θ
2
is the angle of refraction,
and n
1
and n
2
are the respective indices of refraction of the materi-
als.
Procedure
Mount the Light Source, Ray Table Base, and Ray Table on the
Optics Bench. Position the Light Box near the edge of the Ray
Table. Adjust the slit mask on the front of the Light Source so
that one light ray shines across the middle of the top of the Ray
Table.
Place the Rhombus on the center of the table and position it so
the single light ray passes through the parallel sides of the
Rhombus as shown in Figure 5.2. Use a pencil to trace the out-
line of the parallel surfaces of the Rhombus onto the Ray table.
Trace the incident and transmitted rays. Indicate the incoming
and the outgoing rays with arrows in the appropriate directions.
θ
2
θ
1
n
1
n
2
Normal to surface
Refracted Ray (n
2
>
n
1
)
Figure 5.1
P
A
TTERN
LIGHT
SOURCE
COLOR
BULB
: 12V
10W G-4
DO NOT
T
O UCH BULB
WI
TH
FINGERS.
DISCONNECT
PO
WE
R
BEFORE CHAN
GING BULB
. 5 3 1
RA
Y
SLITS
Normal to
Surface
Rhombus
Figure 5.2
θ
ι
Incident
Ray