Gratings
Instructor:
Pro. Lab4
Diffraction Tsai
Jiajie Huo(Jacky)
Member:
Yao Bin Yu
Zeyuan (Seth) Guan
1. introduction.
In this experiment, we are generally focusing on information
about inference and diffraction.
2. Procedure.
a. In section 1, we align the diode laser and shine it through one
of the one- slit gratings on the 3*5 grating plate. Then we choose
the 7th bright spots and the distance from the central maximum
l=1cm.
In Q1, we did the sketch pattern on the graph paper. The orders
we are seeing aroused from both interference and diffraction.
In Q2, we got the experimental width of it was d=0.11mm,
while the real width of it was do=0.088mm, so the difference of
them is 25%.
In Q3, we predicted that when the spectrum would spread out
when the width of the slit decrease and spectrum would be
condense when the width of the slit increase. We changed the
width of the slit to d0=0.176mm and the experimental one was
d=0.228mm, so the difference was 29.5%.
In Q4, the prediction was correct because when we increased the
width of the slit, the spectrum would be condense.
b. Then we shine the laser through a double-slit grating.
In Q5a, we sketched spectrum from the double-slit and the graph
of the intensity of light vs distance from center of the screen. The
experimental slit separation was 0.185mm, the real slit separation
was 0.175mm, so the difference of them was 5.7%.
In Q5b, we predicted that spectrum would spread out when the
slit separation decreased and spectrum would be condensed when
the slit separation increased. We used double-slit the grating with
slit separation of 0.35mm, and the experimental slit separation was
0.31mm, so the difference was 11.4%.
In Q6, the prediction was correct.
c. We shined the laser through several two-slit gratings until we
saw one with a clearly missing order. We record the slit separation
d was 1.35cm and it was the 5th dark spot and 11th bright spot.
In Q7a, the ratio of a/d is 5/11.
In Q7b,
4. Data Sheet
Intensity vs Angle
600
y = 0.0345x 2 - 6.5284x + 547.7
R2 = 0.9423
Int en sit y( lm)
500
400
300
200
100
0
0
50
100
150
angle(relative degree)
Section 3
1st=0degree
3rd=10 degree
Angle(relative)
0
15
30
45
60
75
90
105
120
135
150
165
180
2nd =90degree
max=165lm
Intensity(lm)
165
164
134
114
105
103
106
108
119
123
132
150
172
200
Intensity vs angle
200
180
y = 0.0083x2 - 1.4889x + 170.78
R2 = 0.9482
160
Int en sity( lm)
140
120
100
80
60
40
20
0
0
50
100
150
200
angle (relative angle)
6. Discussion and conclusion.
In this experiment, we have three sections. First, we used one
polarized and found that there was no variation in intensity by only
one polarization. Second, we placed two polarizers and draw the
intensity versus angle graph showing the relationship between the
angle of the two polarizers and the intensity. We found that the
curve was parabola and the parabola is symmetry, as expected. In
section 3, just like the section 2, we added one more polarizer and
do the curve reflecting the relation between intensity and angle.
Again, it was a parabola and it was symmetry, as expected.