Instruction Manual and
Experiment Guide for
the PASCO scientific
Model OS-8529
SLIT ACCESSORY
FOR THE INTRODUCTOR Y AND ADV ANCED
OPTICS SYSTEMS
012-06348A
5/97
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OS-8529
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SINGLE SLIT SET
646-06347-A
OPTICS SYSTEM
SLIT ACCESSORY
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MULTIPLE SLIT SET
646-06347-A
OPTICS SYSTEM
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OS-8529
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© 1997 PASCO scientific $5.00
®
10101 Foothills Blvd. • P.O. Box 619011 • Roseville, CA 95678-9011 USA
Phone (916) 786-3800 • FAX (916) 786-8905 • web: www.pasco.com
better
ways to
teach science
Slit Accessory 012–06348A
012–06348A Slit Accessory
Table of Contents
Section Page
Copyright, Warranty, and Equipment Return ................................................................ ii
Introduction ...................................................................................................................1
Equipment .....................................................................................................................1
Operation ...................................................................................................................... 2
Experiments
Experiment 1: Diffraction from a Single Slit ............................................................. 34
Experiment 2: Interference from a Double Slit .......................................................... 56
Experiment 3: Comparisons of Diffraction and Interference Patterns ........................ 78
Technical Support ........................................................................................ Back Cover
i
Copyright, Warranty , and Equipment Return
PleaseFeel free to duplicate this manual
subject to the copyright restrictions below.
Copyright Notice
The PASCO scientific 012-06348A manual is
copyrighted and all rights reserved. However,
permission is granted to non-profit educational
institutions for reproduction of any part of the Slit
Accessory manual providing the reproductions are
used only for their laboratories and are not sold for
profit. Reproduction under any other circumstances,
without the written consent of PASCO scientific, is
prohibited.
Limited Warranty
PASCO scientific warrants the product to be free from
defects in materials and workmanship for a period of
one year from the date of shipment to the customer.
PASCO will repair or replace, at its option, any part of
the product which is deemed to be defective in
material or workmanship. The warranty does not
cover damage to the product caused by abuse or
improper use. Determination of whether a product
failure is the result of a manufacturing defect or
improper use by the customer shall be made solely by
PASCO scientific. Responsibility for the return of
equipment for warranty repair belongs to the
customer. Equipment must be properly packed to
prevent damage and shipped postage or freight
prepaid. (Damage caused by improper packing of the
equipment for return shipment will not be covered by
the warranty.) Shipping costs for returning the
equipment after repair will be paid by PASCO
scientific.
Equipment Return
Should the product have to be returned to PASCO
scientific for any reason, notify PASCO scientific by
letter, phone, or fax BEFORE returning the product.
Upon notification, the return authorization and
shipping instructions will be promptly issued.
ä
NOTE: NO EQUIPMENT WILL BE
ACCEPTED FOR RETURN WITHOUT AN
AUTHORIZATION FROM PASCO.
When returning equipment for repair, the units must
be packed properly. Carriers will not accept
responsibility for damage caused by improper
packing. To be certain the unit will not be damaged in
shipment, observe the following rules:
➀ The shipping carton must be strong enough for the
item shipped.
➁ Make certain there are at least two inches of packing
material between any point on the apparatus and the
inside walls of the carton.
➂ Make certain that the packing material can not shift in
the box, or become compressed, thus letting the
instrument come in contact with the edge of the
shipping carton.
Address: PASCO scientific
10101 Foothills Blvd.
P.O. Box 619011
Roseville, CA 95678-9011
Credits
Authors: Jon & Ann Hanks
Editor: Sunny Bishop
ii
Phone: (916) 786-3800
FAX: (916) 786-8905
email: techsupp@pasco.com
012–06348A Slit Accessory
Introduction
The PASCO OS-8529 Slit Accessory is designed for use with the
OS-8528 Diode Laser on the optics bench of the Introductory or
Advanced Optics Systems (OS-8500 or OS-9254A). The set of two
➤
disks has many different types of slits for diffraction and interference
experiments. The special comparison patterns have two different slits
spaced close enough together so they can both be illuminated by a single
laser beam at the same time, allowing students to compare the two
NOTE: Due to limitations of the
photographic process used to
produce the slit film, the line and slit
may not be exactly the same width.
different patterns side-by-side.
Equipment
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d= 0.25 0.50
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SINGLE SLIT SET
646-06347-A
OPTICS SYSTEM
SLIT ACCESSORY
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stopper
Single Slit Set Multiple Slit Set
4 single slits (slit widths 0.02, 0.04, 0.08, 0.16 mm)
1 variable slit (slit width varies from 0.02 to 0.20 mm)
1 square pattern
1 hexagonal pattern
1 random opaque dot pattern (dot diameter = 0.06 mm)
1 random hole pattern (hole diameter = 0.06 mm)
1 opaque line of width 0.08 mm
1 slit/line comparison, line and slit have similar width
(0.04 mm)
2 circular apertures (diameters 0.2 mm and 0.4 mm)
base
4 double slits (slit width/separation in mm: 0.04/0.25,
0.04/0.50, 0.08/0.25, 0.08/0.50)
1 variable double slit (slit separation varies from 0.125
to 0.75 mm with constant slit width of 0.04 mm)
4 comparisons: single/double slit with same slit width
(0.04 mm)
double/double slit with same slit width (0.04 mm),
variable separation (0.25 mm 0.50mm)
double/double slit with different slit widths (0.04, 0.08
mm), same separation (0.25 mm)
double/triple slit with same slit width (0.04 mm), same
separation (0.125 mm)
set of 4 multiple slits (2, 3, 4, 5 slits) with same slit width
(0.04 mm), same separation (0.125 mm)
1
Slit Accessory 012–06348A
Operation
laser beam
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SINGLE SLIT SET
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646-06347-A
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SLIT ACCESSORY
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OS-8529
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~7 cm
DIODE LASER
X- Y ADJUSTABLE
OS-8526
VERTICAL
ADJUST
POWER
HORIZONTAL
3.5mm
ADJUST
9 VDC 500mA
ON
OFF
+9VDC
GND
ä
Note: After the initial adjustment,
little or no additional adjustment to
the alignment of the laser beam
with the slit will be required when
you change the slit selection.
~1.5 m
1
Diode Laser
4
➀ Place a slit set and the Diode Laser on the magnetic strips of the
optics bench about 7 cm apart. Position the optics bench so the
Diode Laser is about 1.5 m from a vertical, smooth white
projection surface such as a wall, cardboard, etc.
➁ Align the slit set and the Diode Laser on the optics bench by
abutting the edges of the brackets to the side railing of the optics
bench.
➂ Select the desired slit by rotating the disk until it clicks into place
with the slit at approximately the location of the laser beam on
the disk.
➃ Adjust the alignment of the laser beam with the slit by moving
the laser beam up-and-down and back-and-forth with the vertical
and horizontal adjustment screws until the diffraction pattern on
the projection surface is most intense.
➄ Slide the slit set back-and-forth slightly to find the position that
results in the most intense diffraction pattern.
2
012–06348A Slit Accessory
λ
θ
y
Experiment 1: Diffraction from a Single Slit
Materials required:
• optics bench
• Diode Laser (OS-8528) • metric rule
• Single Slit Set (OS-8529) • page 2 of the Slit Accessory manual
1
From the Introductory or Advanced Optics System (OS-8500 or OS-9254A)
Purpose
The purpose of this experiment is to examine the diffraction pattern formed by laser light
passing through a single slit and verify that the positions of the minima in the diffraction
pattern match the positions predicted by theory.
Theory
1
• white projection surface
When diffraction of light occurs as it passes through
a slit, the angle to the minima in the diffraction
pattern is given by
a sinθ= mλ(m =1,2,3,…)
where a is the slit width,
center of the pattern to the m
wavelength of the light, and m is the order (1 for
the first minimum, 2 for the second minimum, .
. . counting from the center out). See Figure 1.1.
Since the angles are usually small, it can be
assumed that
θ
is the angle from the
th
minimum,
λ
is the
sinθ≈ tan
From trigonometry,
tanθ=
where y is the distance on the screen from the
center of the pattern to the m
the distance from the slit to the screen as shown in
Figure 1.1. The diffraction equation can thus be
solved for the slit width:
D
th
minimum and D is
D
a
θ
slit
screen
Figure 1.1: Single Slit Diffraction Pattern
m = 2
m = 1
m = 1
m = 2
y
a =
(m =1,2,3,…)
y
D
m
3
Slit Accessory 012–06348A
Procedure
➀ Follow the setup procedure on page 2 of the manual using the 0.04
mm slit of the Single Slit Set.
➁ Measure the distance from the slit to the screen and record.
➂ Turn off the room lights and mark the positions of the minima in
the diffraction pattern on the projection surface.
➃ Turn on the room lights and measure the distance between the
first order (m = 1) marks and record this
distance in Table 1.1. Also measure the distance between the
second order (m = 2) marks and record in
Table 1.1.
➄ Make a sketch of the diffraction pattern to scale.
➅ Change the slit width to 0.02 mm and 0.08 mm and make
sketches to scale of each of these diffraction patterns.
Slit-to-screen distance
(D) = _________________
Table 1.1: Data and Results for the 0.04 mm Single Slit
First Order (m=1) Second Order (m=2)
Distance between
side orders
Distance from center
to side (y)
Calculated slit width
% difference
Analysis
➀ Divide the distances between side orders by two to get the distances
from the center of the pattern to the first and second order minima.
Record these values of y in Table 1.1.
➁ Using the average wavelength of the laser (670 nm for the Diode
Laser), calculate the slit width twice, once using first order and
once using second order. Record the results in Table 1.1.
➂ Calculate the percent differences between the experimental slit
widths and 0.04 mm. Record in Table 1.1.
Questions
➀ Does the distance between minima increase or decrease when the
slit width is increased?
4
012–06348A Slit Accessory
Experiment 2: Interference from a Double Slit
Materials required:
• optics bench
• Diode Laser (OS-8528) • metric rule
• Multiple Slit Set (OS-8529) • page 2 of the Slit Accessory manual
1
From the Introductory or Advanced Optics System (OS-8500 or OS-9254A)
Purpose
The purpose of this experiment is to examine the diffraction
and interference patterns formed by laser light passing
through two slits and verify that the positions of the maxima
in the interference pattern match the positions predicted by
theory.
Theory
1
• white projection surface
When light passes through two slits, the two light rays
emerging from the slits interfere with each other and
produce interference fringes. The angle to the maxima
(bright fringes) in the interference pattern is given by
d sin
θ
= mλ
(m = 0, 1, 2, 3 . . .)
where d is the slit separation,
of the pattern to the m
θ
is the angle from the center
th
maximum,
λ
is the wavelength of
the light, and m is the order (0 for the central maximum, 1
for the first side maximum, 2 for the second side maximum,
. . . counting from the center out). See Figure 2.1.
Since the angles are usually small, it can be assumed that
sinθ ≅ tan
From trigonometry,
tanθ=
θ
y
D
where y is the distance on the screen from the center of the
pattern to the m
slits to the screen as shown in Figure 2.1. The interference
equation can thus be solved for the slit separation:
th
maximum and D is the distance from the
D
d
slit
Figure 2.1: Interference Fringes
diffraction minimum
central envelope
θ
screen
m = 2
m =1
m = 0
m = 1
m = 2
m = 4
m = 3
m = 2
m = 1
m = 0
y
d=
(m=0,1,2,3...)
D
m
λ
y
While the interference fringes are created by the interference
of the light coming from the two slits, there is also a
diffraction effect occurring at each slit due to single slit
diffraction, causing the envelope diagramed in Figure 2.2.
dotted line is diffraction envelope
Figure 2.2: Single Slit Diffraction
Envelope
5
Slit Accessory 012–06348A
Procedure
➀ Follow the setup procedure on page 2 of the manual using the
Multiple Slit Set with the 0.04/0.25 mm (slit width/separation)
double slit selected.
➁ Measure the distance from the slit to the screen and record.
➂ Turn off the room lights and mark the positions of the maxima in
the interference pattern on the screen.
➃ Turn on the room lights and measure the distance between the first
order (m = 1) marks and record this distance in Table 2.1. Also
measure the distance between the second order (m = 2) marks and
record in Table 2.1.
Table 2.1: Data and Results for the 0.04/0.25 mm Double Slit
Slit-to-screen distance
(D) = _________________
Questions
➀ Does the distance between maxima
increase, decrease, or stay the same
when the slit separation is
increased?
➁ Does the distance between maxima
increase, decrease, or stay the same
when the slit width is increased?
➂ Does the distance to the first
minima in the diffraction envelope
increase, decrease, or stay the same
when the slit separation is increased?
First Order (m=1) Second Order (m=2)
Distance between
side orders
Distance from center
to side (y)
Calculated slit
separation
% difference
➄ Make a sketch of the interference pattern to scale.
➅ Change to a new double slit with the same slit width (0.04 mm) but
different slit separation (0.50 mm) and make a sketch to scale of this
new interference pattern.
➆ Change to another double slit with a slit width of 0.08 mm and the
original slit separation (0.25 mm) and make a sketch to scale of this
new interference pattern.
Analysis
➀ Divide the distances between side orders by two to get the distances
from the center of the pattern to the first and second order maxima.
Record these values of y in Table 2.1.
➃ Does the distance to the first minima
in the diffraction envelope increase,
decrease, or stay the same when
the slit width is increased?
6
➁ Using the average wavelength of the laser (670 nm for the Diode
Laser), calculate the slit separation twice, once using first order and
once using second order. Record the results in Table 2.1.
➂ Calculate the percent differences between the experimental slit
separation and 0.25 mm. Record in Table 2.1.
012–06348A Slit Accessory
Experiment 3: Comparisons of Diffraction and Interference Patterns
Materials required:
θ
= mλ
1
(m = 1, 2, 3 . . .)
• white projection surface
m = 2
a
m = 1
θ
• optics bench
• Diode Laser (OS-8528) • metric rule
• Single Slit and Multiple Slit Sets (OS-8529) • page 2 of the Slit Accessory manual
1
From the Introductory or Advanced Optics System (OS-8500 or OS-9254A)
Purpose
The purpose of this experiment is to compare the diffraction and interference patterns formed
by laser light passing through various combinations of slits.
Theory
When diffraction of light occurs as it passes through
a slit, the angle to the minima in the diffraction pattern
is given by
a sin
where a is the slit width, θ is the angle from the center
of the pattern to the m
th
minimum, λ is the wavelength
of the light, and m is the order (1 for the first
minimum, 2 for the second minimum, . . . counting
from the center out). See Figure 3.1.
When light passes through two slits, the two light
rays emerging from the slits interfere with each other
and produce interference fringes. The angle to the
maxima (bright fringes) in the interference pattern is
given by
d sin
θ
= mλ
(m = 0, 1, 2, 3 . . .)
where d is the slit separation, θ is the angle from the
center of the pattern to the m
th
maximum,
λ
is the
wavelength of the light, and m is the order (0 for the
central maximum, 1 for the first side maximum, 2 for
the second side maximum, . . . counting from the
center out). See Figure 3.2.
slit
screen
Figure 3.1: Single Slit Diffraction Pattern
m = 5
m = 4
m = 3
θ
d
slit
diffraction envelope
m = 2
m = 1
m = 0
m = 1
m = 2
Figure 3.2: Interference Fringes
screen
7
Slit Accessory 012–06348A
Procedure
➀ Follow the setup procedure on page 2 of the manual using the
Multiple Slit Set with the single-double slit comparison selected.
➁ Sketch the two side-by-side patterns roughly to scale.
➂ Rotate the slit disk to the next comparison set (2 double slits with
the same slit width but different slit separations). Sketch the two
side-by-side patterns roughly to scale.
➃ Rotate the slit disk to the next comparison set (2 double slits with
the same slit separation but different slit widths). Sketch the two
side-by-side patterns roughly to scale.
➄ Rotate the slit disk to the next comparison set (double slits/triple
slits with the same slit separation and same slit widths). Sketch the
two side-by-side patterns roughly to scale.
➅ Replace the Multiple Slit Set with the Single Slit Set. Select the
line/slit comparison. Sketch the two side-by-side patterns roughly
to scale.
➆ Select the dot pattern, and sketch the resulting diffraction pattern
roughly to scale.
➇ Select the hole pattern, and sketch the resulting diffraction pattern
roughly to scale.
Questions
➀ What are the similarities and differences between the single slit
and the double slit?
➁ How does the double slit pattern change when the slit
separation is increased?
➂ How does the double slit pattern change when the slit width is
increased?
➃ What differences are there between a double slit pattern and a
triple slit pattern?
8
T echnical Support
Feedback
If you have any comments about the product or manual,
please let us know. If you have any suggestions on
alternate experiments or find a problem in the manual,
please tell us. PASCO appreciates any customer feedback.
Your input helps us evaluate and improve our product.
To Reach PASCO
For technical support, call us at 1-800-772-8700
(toll-free within the U.S.) or (916) 786-3800.
fax: (916) 786-3292
e-mail: techsupp@pasco.com
web: www.pasco.com
Contacting Technical Support
Before you call the PASCO Technical Support staff, it
would be helpful to prepare the following information:
➤ If your problem is with the PASCO apparatus, note:
Title and model number (usually listed on the
label);
Approximate age of apparatus;
A detailed description of the problem/sequence of
events (in case you cant call PASCO right away, you
wont lose valuable data);
If possible, have the apparatus within reach when
calling to facilitate description of individual parts.
➤ If your problem relates to the instruction manual,
note:
Part number and revision (listed by month and year on
the front cover);
Have the manual at hand to discuss your
questions.
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