Investigation of the possibility of PASCO
scientific science workshop for the experiment :
light Intensity distribution in Single-Slit
diffraction patterns
YUE-SHI(040012006085)
(Department of life science,Ocean University of
China,Qingdao,Shandong,China)
Abstract:
This experiment is very typical. In the traditional class, it’s very
difficult to follow the light intensity distribution. So students can just observe the
graph. But now ,with PASCO ,everything is different. The light intensity distribution
of single-slit diffraction patterns is observed by the combination of a light sensor
and a rotary motion sensor.And make a comparison between the real results and
the theoretical ones to test the possibility of this PASCO light equipment.
Equipment needed:
Science workshop interface 500
LASER
A single-slit
Light sensor
Rotary motion sensor
Aperture Bracket
1.22 m Optics Track
Rotary translator
R
a
α
φ
O
L
chart one
S
l
look at the chart one,
a :the width of the single-slit
φ:衍射角
α:the angel difference of the
adjacent dim lines
R:the distance between O
and aperture bracket
S:length of arc
l:the theoretical distance of
adjacent dim lines.
L: the distance between the
single-slit and aperture
bracket.
1
Theory: The purpose of this laboratory activity is to investigate the wave nature
of light by studying diffraction patterns. Light from a single source falls on a slide
with a single-slit. The diffraction pattern created when monochromatic light passes
through a single slit is similar to the pattern created by a double slit, but central
maximum is measurably brighter than maxima on either side of the pattern. Most of
the light intensity is in the central maximum and very little is in the rest of the
pattern.The smaller the width of the slit, the more intense the central diffraction
maximum. Based on the principles(惠更斯原理），dim lines should meet the following
condition:
sinφ=±
n
a
n   ,when φ is very little(so it is): sinφ≈φ ,
tanφ≈φ,
φ=±
n
a
so the angel difference of two adjacent dim lines:

l
△ φ=
, φ≈tanφ=
a
L
That is, l=Lφ
S=αR (R=14.30cm)
Finally，compare S and l , and investigate how much they are different from each
ather, then change L to see what’s the scope of L in which we can replace the
traditional equipment with this PASCO one.
Data Recording:
1. a ( the width of the single-slit ) and φ
times
recording
1
recording
2
a
(0.01mm)
1
2
3
4
5
6
7
8
9
10
19.0
9.5
9.5
19.7
10.7
9.0
34.8
25.8
9.0
47.1
38.9
8.2
63.2
52.6
10.6
91.5
81.5
10.0
13.9
4.4
9.5
24.4
15.1
9.3
52.5
43.5
9.0
62.8
52.6
10.2
ā
ā=9.40×10 5 m
S(ā)=0.23× 10
5
m
 = 654nm ( this data is given )
φ=  =6.96× 10 3 rad
a
S ( ) S (a )
=
a

S（ φ）=1.7× 10 4 rad
9.4
2. l (the theoretical distance of adjacent dim lines)
2
Lab NO.
1
2
3
4
recording
one
recording
two
3.50
58.99
15.64
58.99
22.84
58.99
25.29
58.99
L( cm)

l( 10
3
m)
(rad)
55.49
43.35
36.15
33.70
3.86
3.02
2.52
2.34
6.96×
10 3
3. α (the angel difference of the adjacent dim lines)
Ps:采样率均为200
Lab 1.
recording
recording
1
2
-100
-122
22
-162
-179
17
59
44
15
123
99
24
115
95
20
188
161
27
128
106
22
212
186
26
97
61
36
182
157
25
α( °）
23.4
α(average)
0.39
0.0068rad
S=αR=0.000973
3
Lab 2.
recording
recording
1
2
77
90
13
119
133
14
101
115
14
147
160
13
93
104
11
129
142
13
117
128
11
153
162
9
129
138
9
162
173
11
α( °）
11.8
α(average)
Lab 3.
0.1967
0.0034rad
S=αR=0.000486m
4
recording
recording
1
2
111
119
8
137
148
11
72
80
8
97
105
8
96
105
9
122
130
8
66
74
8
90
98
8
71
79
8
93
101
8
]
α( °）
8.4
α(average)
0.14
0.00244rad
S=αR=0.000349m
Data analysis and conclusion.
Lab no.
l(m)
S(m)
S-l
(S-l)/l
1
0.000386
0.000973
0.000587
0.603
2
0.000302
0.000486
0.000184
0.379
3
0.000252
0.000349
0.000097
0.278
Obviously,from this chart, S is more and more similarer to l by
lowing L. So this PASCO equipment can replace the traditional
one if L is small enough.
Thusday, April 26, 2007
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