PASCO AP-8586 Laser Speed of Light Apparatus User Manual
Page 9
Laser Speed of Light System
Model No. AP-8586
8
®
arbitrary (but constant) baseline. This elapsed time can be expressed
mathematically as:
(equation 1)
where t
k
is an unknown constant. For the same reason, you can also
measure
instead of
where
(equation 2)
The equation of a line fitted to a plot of
vs.
is
(equation 3)
where c represents the slope of the line. The combinations of
equations 1, 2, and 3 yields
(equation 4)
where K is another arbitrary constant. In equation 4, it is evident that
the slope, c, equals
, which is the speed of light.
Procedure
1. Adjust the alignments of the laser and mirror and the positions of the
lens and receiver to maximize the signal. (Adjust the receiver up,
down, left and right on the carrier, but do not change the position of
the carrier on the bench.)
2. On the oscilloscope, adjust the scale and vertical position of the
signal to maximize the signal trace. Do not change the horizontal
position of the trace.
3. Record the position of the mirror (relative to its initial position) and
the phase of the signal in Table 1a. If your oscilloscope is equipped
with cursors, use them to measure the phase. Otherwise, estimate
the phase to 1/2 of the smallest division on the time scale.
4. Move the mirror back to the next mark and repeat steps 1 through 4.
∆t′
∆t t
k
+
=
d
′
∆d
∆d′
∆d d
k
+
=
∆d′
∆t′
∆d′
c
∆t′
=
∆d
c
∆t K
+
=
∆d ∆t
⁄