Transcript The Speed of Light - San Francisco State University

The Speed of Light
(or How the Laws of Physics are
Slightly Different on the First floor
of Thornton Hall)
Group Members:
• Rich Breazeale
• Jack Young
• Ryan Phelan
Outline
•
•
•
•
The Ultimate Speed
Experimental Setup
Data and Analysis
Conclusion
Our Experiment
Photocell Box
Δx = L / 2
To ext.
trig, laser
To Ch A
Lens
Mirror
To Ch B
HeNe laser
Beam splitter
A
B
Oscilloscope
Our Experiment
A
B
Δt = 0
Δt = a small fraction of a second
Data
μ-s
Time 1
0.2910
0.1530
0.0946
0.0249
-0.0179
Time 2
0.2920
0.1420
0.0862
0.0159
-0.0152
Time 3
0.2890
0.1400
0.0894
0.0190
-0.0124
Distance (m)
97.5
55.1
31.7
13.1
1.17
Average time
0.2907
0.1450
0.0901
0.0199
-0.0152
Standard
Dev
0.0015
0.0070
0.0042
0.0046
0.0028
1/simga^2
428571.4
20408.16
55637.98
47839.26
132216.8
160
90.3333
52
21.5
97.536
55.06718
31.6992
13.1064
# of tiles
Analysis
Delta-t vs. Path Difference
0.35
Difference in path time (microsec.)
0.3
Δt = 0.0031L - 0.0189
0.25
0.2
0.15
0.1
0.05
0
-0.05
0
20
40
60
Difference in path length (m)
80
100
120
Analysis
Our slope: 1/c = 0.0031 microsec./m
c = (3.16 * 10^8 ± 0.04) m/s !
Our c is 1.07 times the usual value for the
speed of light.
The Obvious Conclusion
• The speed of light on the first floor of
Thornton Hall is slightly faster than
elsewhere: c = 3.16 * 10^8 m/s rather than
the usual 3.00 *10^8 m/s.
• This begs the question: does any physical
law apply at the bottom of Thornton Hall?
Fin