OCTOBER 19, 2015
LASER DIFFRACTION
LAB REPORT
ABEL J JAIME (DW5835), JOSHUA KIRBY (FW8822), JAKE AMATO (FX4974)
BE 1310
Tensile Test Lab Report
Page
1
INTRODUCTION
The way that light diffracts can be estimated based on the light’s wavelength and the
geometry of the object that is diffracting the light. Upon diffracting, light is sent at different
levels of intensity. This lab measures the intensity of diffracted light based on position for
different diffraction patters. The goal of the lab is to investigate the relationship between slit
width/pattern spacing, double slit separation and pattern spacing, intensity as a function of
distance for both single and double slit diffraction, and effective light wavelength of all patterns.
MATERIALS

Red Diffraction Laser,

Diffraction Slit System

Dynamics Track

High Sensitivity Light Sensor.

Data-collection Software
METHODS
The dynamics track was set up with the laser on one end and the light sensor on the other.
Once the set up of the dynamics track, laser, and sensor the distance from the sensor to the laser
was measured and recorded. A slide with multiple slits (different quantity, sizes, and spacing)
was provided and it was placed in front of the laser in order to diffract the light. Three trials
were conducted for each of the following:




a = 0.04 one slit
a = 0.08 one slit
a = 0.04 two slits
a = 0.08 two slits
Data for each of the trials is recorded in the Results/Discussion section. Once the slide was
inserted on the appropriate a-value and slit quantity the data-collection software was initiated.
Before data collection, the sensor and software were allowed to calibrate by setting the value of a
white light background to zero intensity. In order to collect accurate data, calibration was
conducted before each sample and each trial. After calibration, data collection was initiated. To
collect the intensity data of the diffracted laser one of the students steadily pulled the sensor
across the track. Pulling the sensor along the track while collecting data yielded the intensity
graphs that are plotted in the Results/Discussion section.
Tensile Test Lab Report
Page
RESULTS / DISCUSSION
Trial
1
2
3
AB
14.85
14.14
14.68
CD
28.32
23.37
25.11
EF
35.80
30.48
38.46
Average AB
Experimental
Value
AB
Theoretical
Value
14.56
14.28
Average AB
Experimental
Value
AB
Theoretical
Value
7.59
7.14
Table 1, a=0.04 , D=0.9, =635
Trial
1
2
3
AB
7.41
7.92
7.43
CD
14.77
15.58
14.52
EF
21.12
22.35
20.87
Table 2, a=0.08 , D=0.9, =635
Trial
1
2
3
Average AB
Experimental
Value
AB
Theoretical
Value
Width of Central
Section
15.02
14.11
14.45
14.53
14.28
AB
Theoretical
Value
7.14
AB
Table 3, a=0.04, d=0.25 , D=0.9, =635
Trial
1
2
3
Average AB
Experimental
Value
Width of Central
Section
7.56
7.34
7.23
7.38
AB
Table 4, a=0.08, d=0.25 , D=0.9, =635
2
Tensile Test Lab Report
Page
Figure 1 - Slit size: a= 0.04
Figure 2 - Slit size: a= 0.08 (Single Slit)
Figure 3 - Slit size: a= 0.04 (Double Slit)
Figure 4 - Slit size: a= 0.08 (Double Slit)
3
Tensile Test Lab Report
Page
4
Laser diffraction can be tested within a lab, but it can also be found through the use of
equations; given in the lab manual are several equations that can be used to theoretically find the
width of the center sections of the graphs. This lab requires the knowledge of the wavelength (λ)
of the laser, the slit width (a), the angle from the center pattern to m (θ), and the maximum
intensity (Im). Through the use of these variable the theoretical peak distances can be found and
compared to the results found through the trial of each diffraction to see the consistencies and
inconsistencies between the two.
Through the use of the Diffraction Apparatus, it is seen that the differences in the single
and double slit diffractions have a large difference; while the single slit diffractions (using λL/a)
shows one large peak with several smaller hills, the double slit diffractions (using λL/d) show
many peaks and valleys on the graphs. While the results of these graphs may vary from error, the
overall shape of the graphs should be very similar to the results shown above. Some examples of
what may have been a cause for the changes in these graphs may be the speed in which the light
sensor was moved across the track; if the sensor was moved too quickly, the results of that
change in speed would give the apparatus not enough time for it to collect data. Because this type
of problem may occur, the lab asks the user to take approximately thirty seconds to finish each
trial. Another way the results may be skewered is the lack of properly calibrating the apparatus to
start at an intensity of zero percent. This will cause a change in the collection of the data causing
the graph to shift along the “Intensity” axis (y-axis). These result will not only shift the graph but
cause the results to differ from the theoretical data for the central sections of the graphs
positioning; without perfect conditions, the results will differ from the theoretical data found
through the use of the equations of laser diffraction.
CONCLUSION
This lab successfully measured the intensity vs. position for double slit and single slit
diffraction. Graphs that plotted the position vs. intensity for each of the runs matched the
theoretical calculations.
Tensile Test Lab Report
Page
5
CITATIONS
Callister, W. (2005). Fundamentals of materials science and engineering: An integrated approach
(2nd ed.). Hoboken, NJ: John Wiley & Sons.
Diffraction Apparatus order cod DAK, Vernier Software & Technology, 2014
Tensile Test Lab Report
Page
APPENDIX
Matlab Code:
%Graphing of the different sample information. Change the lxsread () information, boundaries,
and labels for the different test samples.
[t1] = xlsread('double .08 trial 1.csv', 'double .08 trial 1', 'B66:C349');
I1 = t1(:,1);
P1= t1(:,2);
subplot(1,3,1)
plot(P1, I1)
ylim([-.1 45])
title('.08 trial 1')
ylabel('Intensity %')
xlabel('Position (mm)')
[t2] = xlsread('double .08 trial 2.csv', 'double .08 trial 2', 'B83:C329');
I2 = t2(:,1);
P2= t2(:,2);
subplot(1,3,2)
plot(P2, I2)
ylim([-.1 45])
title('.08 trial 2')
ylabel('Intensity %')
xlabel('Position (mm)')
[t3] = xlsread('double .08 trial 3.csv', 'double .08 trial 3', 'B67:C336');
I3 = t3(:,1);
P3= t3(:,2);
subplot(1,3,3)
plot(P3, I3)
ylim([-.1 45])
title('.08 trial 3')
ylabel('Intensity %')
xlabel('Position (mm)')
%calculations for finding the AB theoretical Data
function[AB] = functAB(w,D,a)
AB = (w*10^-3*D)/(a);
end
functAB(635, 0.9, 0.04)
ans =
14.2875
>> functAB(635, 0.9, 0.08)
ans =
7.1437
a = 0.04 or 0.08; %laser slit distance in meters.
Lam = 635; %Wavelength
m = 7.27;
D = 110; %cm
y = (m.*Lam.*D)./a;
Y1 = (900.*(635.*10.^-9)) / (.04.*10.^-2).*(1);
6
istribution of the patterns, or as a simpler search for the locations of
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Page
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Warranty
Vernier warrants this product to be free from defects in
a period of five years from the date of shipment to the c
Warranty
not cover
damage
the product
by defects
abuse orinimp
Vernier
warrants
thistoproduct
to be caused
free from
ma
a period of five years from the date of shipment to the cust
not cover damage to the product caused by abuse or impro