Pasco Scientific OS-8523 User manual

Instruction Manual and
Experiment Guide for
the PASCO scientific
Model OS-8523
012-05880B
3/97
©1997 PASCO scientific $5.00
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OS-8523
SINGLE SLIT SET
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BASIC OPTICS
SLIT ACCESSORY
646-05865-B
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BASIC OPTICS
SLITACCESSORY
OS-8523
MULTIPLESLIT SET
646-05865-B
SLIT ACCESSORY
FOR THE BASIC OPTICS SYSTEM

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012-05880B Slit Accessory
Table of Contents
Section Page
Copyright, Warranty, and Equipment Return .....................................................ii
Introduction ......................................................................................................1
Equipment ........................................................................................................2
Assembly..........................................................................................................3
Experiments
Exp. 1: Diffraction from a Single Slit ..........................................................5
Exp. 2: Interference from a Double Slit .......................................................9
Exp. 3: Comparisons of Diffraction and Interference Patterns .....................13
Technical Support ......................................................................... Inside Back Cover

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Slit Accessory 012-05880B
Copyright Notice
The PASCO scientific Model OS-8523 Slit Accessory
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.
Copyright, Warranty and Equipment Return
Please—Feel free to duplicate this manual
subject to the copyright restrictions below.
Credits
Authors: Ann & Jon Hanks
Editor: Sunny Bishop
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.
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:
➀The packing carton must be strong enough for the
item shipped.
➁Make certain there are at least two inches of
packing material between any point on the
apparatus and the inside walls of the carton.
➂Make certain that the packing material cannot shift
in the box or become compressed, allowing the
instrument come in contact with the packing
carton.
Address: PASCO scientific
10101 Foothills Blvd.
Roseville, CA 95747-7100
Phone: [phone]
FAX: [phone]
email: [email protected]
web: www.pasco.com
ä NOTE: NO EQUIPMENT WILL BE
ACCEPTED FOR RETURN WITHOUT AN
AUTHORIZATION FROM PASCO.

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012-05880B Slit Accessory
Introduction
The PASCO OS-8523 Slit Accessory is used with the
PASCO OS-8525 Laser Diode on the optics bench in the
PASCO OS-8515 Basic Optics System. This 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. This allows the student to
compare the two different patterns side-by-side so they
can see their similarities and differences.
OS-8523 Slit Accessory specifications:
The contents of the Single Slit Disk are: (See Figure 1)
– 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)
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BASIC OPTICS
SLIT ACCESSORY
OS-8523
SINGLE SLIT SET
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646-05865
Figure 1: Single Slit Disk
➤ 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.
The contents of the Multiple Slit Disk are: (See Figure 2)
– 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 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),
different separation (0.25 mm/0.50 mm)
– 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)
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BASIC OPTICS
SLIT ACCESSORY
OS-8523
MULTIPLE SLIT SET
a= 0.04 0.04
d= 0.25
a= 0.04 0.04
d= 0.25 0.50
a= 0.04 0.08
d= 0.25 0.25
a= 0.04 0.04
d= 0.125 0.125
646-05865
Figure 2: Multiple Slit Disk

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Slit Accessory 012-05880B
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OS-8523
SINGLE SLIT SET
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BASIC OPTICS
SLIT ACCESSORY
646-05865-B
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BASIC OPTICS
SLIT ACCESSORY
OS-8523
MULTIPLE SLIT SET
646-05865-B
Equipment
OS-8523 Slit Accessory Equipment
The OS-8523 Slit Accessory includes the following:
– Single Slit Disk
– Multiple Slit Disk
– lens holder with thumbscrew (2)
lens holder with
thumbscrew (2)
Single Slit Disk Multiple Slit Disk

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012-05880B Slit Accessory
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BASIC OPTICS
SLIT ACCESSORY
OS-8523
SINGLE SLIT SET
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Assembly
Mounting the Slit Accessory to the Optics
Bench
Each of the slit disks is mounted on a ring which snaps
into an empty lens holder. The ring should be rotated in
the lens holder so the slits at the center of the ring are
vertical in the holder. See Figure 3. Tighten the thumb-
screw on the holder so the ring cannot rotate during use.
To select the desired slits, rotate the disk until it clicks
into place with the desired slits at the center of the holder.
➤ NOTE: All slits are vertical EXCEPT the
comparison slits which are horizontal. The com-
parison slits are purposely horizontal because the
wide laser diode beam will cover both slits to be
compared. If you try to rotate these slits to the
vertical position, the laser beam may not be large
enough to illuminate both slits at the same time.
To align the laser beam and the slits, place the Diode
Laser (OS-8525) at one end of the bench. Place the slit
holder on the optics bench a few centimeters from the
laser with the disk-side of the holder closest to the laser.
Figure 3: Slit Accessory and Lens Holder
ring
lens holder
slit disk
attachment
thumbscrew
See Figure 3. Plug in the Diode Laser and turn it on.
Adjust the position of the laser beam from left-to-right
and up-and-down until the beam is centered on the slit.
Once this position is set, it is not necessary to make any
further adjustments of the laser beam when viewing any
of the slits on the disk. When you rotate the disk to a new
slit, the laser beam will be already aligned. The slits click
into place so you can easily change from one slit to the
next, even in the dark.
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OS-8523
SINGLESLITSET
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BASIC OPTICS
SLIT ACCESSORY
646-05865-B
Laser Light
Avoid Direct Eye
Exposure
Laser Diode
DANGER
optics bench
mounted slit
accessory OS-8525
Diode Laser
adjusting
screws
input jack
(9VDC)
Figure 4: Using the Slit Accessory
with the Diode Laser

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Slit Accessory 012-05880B
Notes:

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012-05880B Slit Accessory
Experiment 1: Diffraction from a Single Slit
EQUIPMENT REQUIRED
– track and screen from the Basic Optics System (OS-8515)
– Diode Laser (OS-8525)
– Single Slit Disk (OS-8523)
– white paper to cover screen
– metric rule
Purpose
The purpose of this experiment is to examine the diffraction pattern formed by laser light pass-
ing through a single slit and verify that the positions of the minima in the diffraction pattern
match the positions predicted by theory.
Theory
When diffraction of light occurs as it passes through a slit, the angle to the minima in the diffrac-
tion pattern is given by
asin θ =m λ (m=1,2,3,…)
where ais the slit width, θ is the angle from the cen-
ter of the pattern to the mth minimum, λ is the wave-
length of the light, and mis 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
sin θ ≈tan
θ
From trigonometry,
tan θ =
y
D
where yis the distance on the screen from the center
of the pattern to the mth minimum and Dis 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:
a=m
λ
D
y(m=1,2,3,…)
θ
D
a
slit
screen
Figure 1.1: Single Slit Diffraction Pattern
m = 2
m = 1
m = 2
m = 1 y

Slit Accessory 012-05880B
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Setup
➀Set up the laser at one end of the optics bench and place the Single Slit Disk in its holder about 3
cm in front of the laser. See Figure 1.2.
➁Cover the screen with a sheet of paper and attach it to the other end of the bench so that the paper
faces the laser.
➂Select the 0.04 mm slit by rotating the slit disk until the 0.04 mm slit is centered in the slit holder.
Adjust the position of the laser beam from left-to-right and up-and-down until the beam is cen-
tered on the slit.
Figure 1.2: Optics Bench Setup
Procedure
➀Determine the distance from the slit to the screen. Note that the slit is actually offset from the
center line of the slit holder. Record the screen position, slit position, and the difference between
these (the slit-to-screen distance) in Table 1.1.
➁Turn off the room lights and mark the positions of the minima in the diffraction pattern on the
screen.
➂Turn 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.
laser screen
slit
Table 1.1: Data and Results for the 0.04 mm Single Slit
Slit-to-screen distance (D) = _____________________________
First Order (m=1) Second Order (m=2)
Distance between
side orders
Distance from center
to side (y)
Calculated slit width
% difference

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012-05880B Slit Accessory
➃Make a sketch of the diffraction pattern to scale.
➄Change the slit width to 0.02 mm and 0.08 mm and make sketches to scale of each of these
diffraction patterns.
Analysis
➀Divide the distances between side orders by two to get the distances from the center of the pat-
tern to the first and second order minima. Record these values of yin Table 1.1.
➁Using 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.
➂Calculate the percent differences between the experimental slit widths and 0.04 mm. Record in
Table 1.1.
Questions
➀Does the distance between minima increase or decrease when the slit width is increased?

Slit Accessory 012-05880B
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Notes:

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012-05880B Slit Accessory
Experiment 2: Interference from a Double Slit
EQUIPMENT REQUIRED
– track and screen from the Basic Optics System (OS-8515)
– Diode Laser (OS-8525)
– Multiple Slit Disk (OS-8523)
– white paper to cover screen
– metric rule
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 interfer-
ence pattern match the positions predicted by theory.
Theory
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
dsin θ =m λ (m=0,1,2,3,…)
where dis the slit separation, θ is the angle from the
center of the pattern to the mth maximum, λ is the
wavelength of the light, and mis 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
sin θ ≈tan
θ
From trigonometry,
tan θ =
y
D
where yis the distance on the screen from the center of the
pattern to the mth maximum and Dis the distance from the
slits to the screen as shown in Figure 2.1. The interference
equation can thus be solved for the slit separation:
d=m
λ
D
y(m=0,1,2,3,…)
Figure 2.2: Single Slit Diffraction Envelope
Figure 2.1: Interference Fringes
D
d
screen
slit
central envelope
dotted line is diffraction envelope
m = 1
m = 0
m = 2
m = 3
m = 4
diffraction minimum
y
m = 1
m = 2
m = 2
m = 1
m = 0
θ

Slit Accessory 012-05880B
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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. This
causes the envelope as seen in Figure 2.2.
Setup
➀Set up the laser at one end of the optics bench and place the Multiple Slit Disk in its holder about
3 cm in front of the laser. See Figure 2.3.
➁Cover the screen with a sheet of paper and attach it to the other end of the bench so that the paper
faces the laser.
➂Select the double slit with 0.04 mm slit width and 0.25 mm slit separation by rotating the slit disk
until the desired double slit is centered in the slit holder. Adjust the position of the laser beam
from left-to-right and up-and-down until the beam is centered on the double slit.
Procedure
➀Determine the distance from the slits to the screen.
Note that the slits are actually offset from the center line of the slit holder. Record the screen
position, slit position, and the difference between these (the slit-to-screen distance) in Table 2.1.
➁Turn off the room lights and mark the positions of the maxima in the interference pattern on the
screen.
➂Turn 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 mm/0.25 mm Double Slit
laser screen
slit
Figure 2.3: Optics Bench Setup
Slit-to-screen distance (D) = _________________
First Order (m=1) Second Order (m=2)
Distance between
side orders
Distance from center
to side (y)
Calculated slit
separation
% difference

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012-05880B Slit Accessory
➃Make a sketch of the interference pattern to scale.
➄Change 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.
➅Change 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
➀Divide 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 yin Table 2.1.
➁Using the average wavelength of the laser (670 nm for the Diode Laser), calculate the slit
1separation twice, once using first order and once using second order. Record the results in
Table 2.1.
➂Calculate the percent differences between the experimental slit separation and 0.25 mm. Record
in Table 2.1.
Questions
➀Does the distance between maxima increase, decrease, or stay the same when the slit separation
is increased?
➁Does the distance between maxima increase, decrease, or stay the same when the slit width is
increased?

Slit Accessory 012-05880B
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➂Does the distance to the first minima in the diffraction envelope increase, decrease, or stay the
same when the slit separation is increased?
➃Does the distance to the first minima in the diffraction envelope increase, decrease, or stay the
same when the slit width is increased?

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012-05880B Slit Accessory
Figure 3.1: Single Slit Diffraction Pattern
a
screen
slit
EQUIPMENT REQUIRED
– track and screen from the Basic Optics System (OS-8515)
– Diode Laser (OS-8525)
– Single and Multiple Slit Disks (OS-8523)
– white paper to cover screen
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 diffrac-
tion pattern is given by
asin θ =m λ (m=1,2,3,…)
where ais the slit width, θ is the angle from the
center of the pattern to the mth minimum, λ is the
wavelength of the light, and mis 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 pat-
tern is given by
dsin θ =m λ (m= 0, 1, 2 , 3,...)
where dis the slit separation, θ is the angle from the
center of the pattern to the mth maximum, λ is the
wavelength of the light, and mis 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.
Setup
➀Set up the laser at one end of the optics bench and
place the Multiple Slit Disk in its holder about 3
cm in front of the laser. See Figure 3.3.
m = 2
m = 1
m = 2
m = 1
dθ
diffraction envelope
slit
θ
screen
Figure 3.2: Interference Fringes
m = 0
m = 5
m = 1
m = 2
m = 3
m = 4
Experiment 3: Comparisons of Diffraction and Interference Patterns

Slit Accessory 012-05880B
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➁Cover the screen with a sheet of paper and attach it to the other end of the bench so that the paper
faces the laser.
➂Select the single-double slit comparison by rotating the slit disk until the desired slit set is
centered in the slit holder. Adjust the position of the laser beam from left-to-right and up-and-
down until the beam is centered on the slit set so that both the single slit and the double slit are
illuminated simultaneously. The patterns from the single and double slits should be vertical and
side-by-side on the screen.
Procedure
➀Sketch the two side-by-side patterns roughly to scale.
➁Rotate 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.
➂Rotate 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.
➃Rotate the slit disk to the next comparison set (double slits/triple slits with the same slit separa-
tion and same slit widths). Sketch the two side-by-side patterns roughly to scale.
laser screen
slit
Figure 3.3: Optics Bench Setup

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012-05880B Slit Accessory
➄Replace the Multiple Slit Disk with the Single Slit Disk. Select the line/slit comparison. Sketch
the two side-by-side patterns roughly to scale.
➅Select the dot pattern on the Single Slit Disk. Sketch the resulting diffraction pattern roughly to
scale.
➆Select the hole pattern on the Single Slit Disk. Sketch the resulting diffraction pattern roughly to
scale.
Questions
➀What are the similarities and differences between the single slit and the double slit?
➁How does the double slit pattern change when the slit separation is increased?
➂How does the double slit pattern change when the slit width is increased?
➃What differences are there between a double slit pattern and a triple slit pattern?

Slit Accessory 012-05880B
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➄How does the diffraction pattern from a slit differ from the diffraction pattern from a line?
➅How does the diffraction pattern from the dot pattern differ from the diffraction pattern from the
hole pattern?