Lab 5 Double Slit Interference Pattern
The Purpose
The purpose of this lab was to study the interference pattern of light using an imaginary double
slut experiment.
The Experiment
This is a fictitious experiment. Double Slit Interference Pattern
The distance between the locations of the minima (dark spots) on a screen is measured, Δy .
The slit to screen distance is 2.3m and the wavelength is 650nm.
The Theory
The purpose of this experiment is to experimentally verify the wavelength of a laser using a
double slit interference pattern projected on the wall.
We assume three things about the experiment:
• That the light entering the slits is coherent, that is they maintain a constant phase
relationship with one another.
• The light entering the slits is monochromatic; there is only one wavelength of light that
is being scattered.
• The distance from the slits to the screen is much greater than the distance between the
slits. That is: L>>d
From the third assumption, it gives rise to an important consequence. Since L>>d the rays
reaching the screen are essentially parallel for the purposes of computation. This creates a right
triangle with hypotenuse d which will give us an easy expression for the path difference:
∆y = d. sin(Θ)
The Data
Delta y (mm) d (m)
3.76 0.000397606383
3.94 0.0003794416244
3.52 0.0004247159091
3.79 0.0003944591029
4.07 0.0003673218673
3.98 0.0003756281407
3.62 0.0004129834254
The Analysis
Average
0.0003931652075 m
Standard Deviation 0.00002070978197 m
Confidence Interval 0.00002738863883 m
d max
0.0004205538464 m
d min
0.0003657765687 m
The Conclusion
From this experiment we were able to measure the distance between the locations of the
minima on a screen. The average value of the distance between the spots was 0.0003932 +0.00002071 m. The maximum and minimum values of the specific heat are therefore
0.00042055 m and 0.00036578 m, respectively.