PASCO OS-8533A User Manual

Instruction Manual and
012-09200A
Experiment Guide for the PASCO scientific Model OS-8533A
POLARIZATION ANALYZER
Light Sensor
Polarization
Analyzer
© 2005 PASCO scientific
Aperture
Bracket
012-09200A Polarization Analyzer
Table of Contents
Section Page
Copyright, Warranty, and Equipment Return.....................................................ii
Description .......................................................................................................1
Mounting a Rotary Motion Sensor ....................................................................1
Using the Rotary Motion Sensor ....................................................................... 3
Mounting a Light Sensor...................................................................................3
Setup for Measuring Light Intensity ..................................................................4
Verify Malus’ Law of Polarization ....................................................................5
Teacher’s Guide................................................................................................9
Technical Support ......................................................................... Inside Back Cover
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Polarization Analyzer 012-09200A
Copyright, Warranty, and Equipment Return
Please—Feel free to duplicate this manual subject to the copyright restrictions below.
Copyright Notice
The PASCO scientific 012-09200 Model OS-8533A Polarization Analyzer is copyrighted and all rights reserved. However, permission is granted to non-profit educational institutions for reproduction of any part of the 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
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.
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:
The packing carton must be strong enough for the
item shipped.
Make certain there are at least two inches of
packing material between any point on the appara­tus and the inside walls of the carton.
Make 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
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.
Credits
This manual authored by: Dave Griffith
Phone: (916) 786-3800 FAX: (916) 786-3292 email: techsupp@pasco.com web: www.pasco.com
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012-09200A Polarization Analyzer
Introduction
The PASCO OS-8533A Polarization Analyzer is designed to be mounted on the Optics Bench of the OS-8515 Basic Optics System and to be used with the Basic Optics Light Source (part of the OS-8515 Basic Optics Sys­tem) and a Light Sensor such as the PASCO CI-6504A, or PS-2106 to explore polarization. When used with the PASCO CI-6538 or PS-2120 Rotary Motion Sensor, you can measure the relationship between the light inten­sity transmitted through a set of polarizers and the angle of the polarizers.
Recommended Equipment
Basic Optics System (OS-8515) Light Sensor (CI-6504A or PS-2106) Rotary Motion Sensor (CI-6538, or PS-2120)
Description
The Polarization Analyzer consists of a Po­larizer Holder, an Accessory Holder with Mounting Bracket, two Polarizers, a Retarder and an Aperature Bracket. The mounting bracket is permanently attached to the Acces­sory Holder. The mounting bracket holds a Rotary Motion Sensor in position to measure the angle of one Polarizer as it turns relative to the other Polarizer. The mounting bracket includes two thumbscrews and a plastic belt. The thumbscrews attach the Rotary Motion Sensor to the bracket. The plastic belt is used with a Rotary Motion Sensor.
The Polarizers and Retarder snap into the opening at the top of the Accessory Holder or the Polarizer Holder. The Retarder is a one-quarter wavelength (140 nanometer) re­tarder. Each Polarizer has an angular scale near its outside edge marked in ten degree increments with additional marks at 45, 135, 225, and 315 degrees.
Polarizer with
Groove
Accessory Holder with
Mounting Bracket
thumbscrew
storage holes
Figure 1: Polarization Analyzer Components
Polarizer Holder
plastic belt
thumbscrews
Polarizer
Retarder
One of the Polarizers has a groove on its front edge. Use this Polarizer with the Accessory Holder. When the Ro­tary Motion Sensor is mounted on the Accessory Holder bracket, you can put the plastic belt over the groove on the front of the Polarizer and a groove on the three-step pulley on the Rotary Motion Sensor. This allows you to measure the angular position of the Polarizer as it turns.
Mounting a Rotary Motion Sensor
Prepare the Rotary Motion Sensor
You will need a Phillips head screwdriver with a small tip (e.g., #1).
The Rotary Motion Sensor comes with a rod clamp
Rotary Motion Sensor
rod clamp
Remove two
screws from the
rod clamp.
Phillips head screwriver
Figure 2: Remove Rod Clamp
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Polarization Analyzer 012-09200A
attached to one end. Use a Phillips head screwdriver to loosen the two screws that hold the rod clamp. Remove the rod clamp and screws. (Please put the rod clamp and screws in a safe place for future use.)
“O” ring
The Rotary Motion Sensor also comes with a rubber “O” ring in the largest groove of the three-step pulley that is attached to the sensor’s shaft. Remove the “O” ring from the three-step pulley and put the ring in a safe place for future use. The sensor is now ready to mount on the Accessory Holder bracket.
Prepare the Mounting Bracket
The bracket comes with two thumb­screws stored in threaded holes on the side of the bracket. Remove the
Accessory Holder
two thumbscrews and set them aside for now. The bracket also holds the plastic belt. The belt is wrapped twice around
Mounting Bracket
two semi-circular notches on the top and bottom edges of the bracket. Unwrap the belt from the notches and set it aside for now.
plastic belt
thumbscrews
Attach the Rotary Motion Sensor
Turn the Rotary Motion
Accessory Holder
Mounting Bracket
Figure 4: Prepare Bracket
Sensor so the three-step pulley faces the Accessory Holder and the threaded
holes in the end of the sensor line up with the holes of the Mounting Bracket. Use the two thumbscrews to attach the Rotary Motion Sensor to the Mounting Bracket.
three-step pulley
Rotary Motion Sensor
Figure 3: Remove “O” Ring
three-step pulley
thumbscrews
Put on the Plastic Belt
Loop the bottom of the plastic belt around the three-step
pulley of the Rotary Motion Sensor so the bottom of the belt is in the large-diameter groove of the step-
plastic belt
pulley.
Attach the Polarizer
three-step pulley
Get the Polarizer that has the groove on its front edge. Slip the top of the plastic belt into the groove on the front edge of the Polarizer. Snap the Polarizer into place
Rotary Motion Sensor
Figure 6: Put on Plastic Belt
on the Accessory Holder.
Rotary Motion Sensor
Figure 5: Attach Sensor to Bracket
Polarizer with Groove
plastic belt
Figure 7: Attach Polarizer
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012-09200A Polarization Analyzer
Using the Rotary Motion Sensor
Mount the Accessory Holder on the Optics Bench
The Accessory Holder snaps into the Optics Bench. To move the Accessory Holder along the bench, grasp the base of the holder and squeeze the locking clip inward. Continue to squeeze inward on the locking clip as you move the holder to a new position. When you release the locking clip, the Accessory Holder is held
firmly in place.
Rotate the Polarizer
Rotate the Polarizer by grasping the edge
Polarizer
of the Polarizer. As you turn the Polar­izer, the plastic belt will turn the three­step pulley on the Rotary Motion Sensor by the same amount. When the Rotary Motion Sensor is connected to ScienceWorkshop or PASPORT interface, you
Rotary Motion
Sensor
can measure the angular position of the Polarizer to within one-quarter degree.
Polarizer
Rotary Motion
Accessory
Holder
locking clip
Optics Bench
Figure 8: Holder on Bench
Sensor
position
indicator
Figure 9: Rotate the Polarizer
Aperature Bracket
The Aperture Bracket has two main components: the Light
locking clip
Aperture Bracket
Holder
Sensor Mount and the Aperture Bracket Holder.
Light Sensor Mount
The Light Sensor Mount has an Aperture Bracket Screen, an Aperture Disk, a large thumbscrew, and a threaded post. You can use either the large thumbscrew or the threaded post to
Optics Bench
attach a Light Sensor to the Light Sensor Mount in one of two positions. Use the threaded post if you want to hold the Light Sensor Mount in a rod clamp. The large thumbscrew or the post is stored in the threaded storage hole on the Light Sensor Mount when not in use.
Aperture Bracket Holder
position
indicator
Figure 10: Holder on Bench
Two metal thumbscrews attach the Aperture Bracket Holder to the back of the Light Sensor Mount. The Aperture Bracket Holder snaps into place anywhere along the center section of the Optics Bench that is part of the OS-8515 Basic Optics System. To move the holder along the bench, grasp the base of the holder and squeeze the locking clip inward. Continue to squeeze inward on the locking clip as you move the holder to the new position. When you release the locking clip, the holder is held firmly in place.
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Polarization Analyzer 012-09200A
Aperture Bracket Screen
The Aperture Bracket Screen is designed to help you align the Aperture Disk with a light source. Two small thumbscrews attach the Aperture Bracket Screen to the front of the Light Sensor Mount.
Aperture Disk
The Aperture Disk has three circular apertures and six slit apertures (numbered one through six). The slit widths are as follows:
1 = 0.1 mm 2 = 0.2 mm 3 = 0.3 mm 4 = 0.5 mm 5 = 1.0 mm 6 = 1.5 mm
One circular aperture is 8 mm in diameter, the
Aperture Disk
same dimension as the opening of the PASCO Model CI-6504A, CI-6604, or PS-2106 Light Sensor. A second circular aperture has the same diameter but has a grid pattern of small holes (0.25 mm diameter) that allows 10% transmission of light through the aperture. The third circular aperture is 2 mm in diameter, or one-fourth the diameter of the larger circular apertures, and translucent.
slit apertures
(1 - 6)
Aperture Bracket
Screen
5
6
4
3
10%
2
1
circular
apertures
The Aperture Disk can be rotated to any of the nine positions to put one of the slits or circular apertures
Figure 11: Aperture Disk
in line with a Light Sensor mounted behind the Aperture Disk.
Using the Aperature Bracket
Mounting a Light Sensor
Aperture
Aperture Bracket
Holder
Light Sensor
Light Sensor Mount
Light Sensor
You can use the Aperture Bracket to mount a Light Sensor on the Optics Bench. You can use the Light Sensor to measure the intensity of light through the Polarizers as you rotate one Polarizer relative to the other.
Use either the large thumbscrew or the post to mount a Light Sensor to the Light
Aperture Disk
Light Sensor
large thumbscrew
into front hole
Sensor Mount. Position the Light Sensor on top of the Light Sensor Mount so the hole in the bottom of the sensor is in line with the front hole in the mount and the opening of the Light Sensor touches the
Figure 12: Mount the
Light Sensor
Figure 13: Light Sensor
onto Mount
vertical part of the Light Sensor Mount. Put the threaded end of the thumbscrew or post through the hole and turn the thumbscrew or post clock­wise to tighten. See Figure 12 & 13.
Snap the Aperture Bracket Holder into the Optics Bench.Rotate the Aperture Disk so the open circular aperture is in line with the opening to the Light Sensor.
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012-09200A Polarization Analyzer
Setup for Measuring Light Intensity
You can use the Basic Optics Bench, Basic Optics Light Source, Polarization Analyzer, Rotary Motion Sensor, Aperture Bracket,
Polarizer Mount
and a Light Sensor to measure the light intensity through the Polarizers as one Polarizer is rotated relative to the other.
Prepare the Polarizer
Put the second Polarizer in the empty Polarizer Mount that comes with the Polarization Analyzer.
Mount the Light Source
Put the Basic Optics Light Source at one end of the Basic Optics Bench. Refer to the OS-8515 instructions. Turn the Light Source so it produces a “point source” of light that is aimed toward the other end of the bench.
Mount the Polarization Analyzer
Snap the Polarizer Mount onto the Optics Bench. Snap the Polar­ization Analyzer with Rotary Motion Sensor onto the Optics Bench.
Mount the Light Sensor
Basic Optics Light Source
Polarizer Holder
Snap the Aperture Bracket Holder with the Light Sensor onto the Optics Bench with the Light Sensor opening toward the Light Source
POLARIZER MOUNT
Polarizer
Figure 14: Prepare Polarizer
Light Sensor
Aperture Bracket
Holder
Polarization Analyzer with
Rotary Motion Sensor
Figure 15: Setup for Measuring Light Intensity
5
Optics Bench
Polarization Analyzer 012-09200A
Notes:
6
E=E
φ
I=I
0
φ
012-09200A Polarization Analyzer
V erify Malus’ Law of Polarization
EQUIPMENT NEEDED
– Basic Optics Bench (part of OS-8515) – Light Sensor (CI-6504A or PS-2106) – Basic Optics Light Source (part of OS-8515) – Rotary Motion Sensor (CI-6538 or PS-2120) – Polarization Analyzer with Aperture Bracket (OS-8533A)
Introduction
The purpose of this laboratory activity is to determine the relationship between the intensity of the transmitted light through two polarizers and the angle, Ø, of the axes of the two polarizers.
Theory
A polarizer only allows light which is vibrating
Polarizer 2
0
cos
in a particular plane to pass through it. This plane
Polarizer 1
forms the “axis” of polarization. Unpolarized light vibrates in all planes perpendicular to the direction of propagation. If unpolarized light is incident upon an “ideal” polarizer, only half will be transmitted through the polarizer. Since in reality no polarizer is “ideal”, less than half the
2
light will be transmitted.
unpolarized light
polarized light, I
The transmitted light is polarized in one plane. If this polarized light is incident upon a second polarizer, the axis of which is oriented such that it is perpendicular to the plane of polarization of the incident light, no light will be transmitted through the second polarizer.
However, if the second polarizer is oriented at an angle so that it is not perpendicular to the first polarizer, there will be some component of the
component of polarized light parallel to
axis of Polarizer 2
Figure 1.1: Polarization
electric field of the polarized light that lies in the same direction as the axis of the second polarizer, thus some light will be transmitted through the second polarizer (see the bottom figure).
φ
I = I0cos2 φ
The component, E, of the polarized electric field, E
, is found by:
o
cos
0
Since the intensity of the light varies as the square of the electric field, the light intensity transmitted through the second filter is given by:
where Io is the intensity of the light passing through the first filter and Ø is the angle between the polarization axes of the two filters.
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Polarization Analyzer 012-09200A
PASCO
scientific
Consider the two extreme cases illustrated by this equation:
2
If Ø is zero, the second polarizer is aligned with the first polarizer, and the value of cos
Ø is one. Thus the
intensity transmitted by the second filter is equal to the light intensity that passes through the first filter. This case will allow maximum intensity to pass through.
If Ø is 90º, the second polarizer is oriented perpendicular to the plane of polarization of the first filter, and the
2
(90º) gives zero. Thus no light is transmitted through the second filter. This case will allow minimum inten-
cos sity to pass through.
These results assume that the only absorption of light is due to polarizer effects. In fact most polarizing films are not clear and thus there is also some absorption of light due to the coloring of the Polaroid filters.
Procedure
In this activity, the Light Sensor measures the relative intensity of light that passes through two polarizers. You will change the angle of the second polarizer relative to the first. The Rotary Motion Sensor measures the angle.
The DataStudio records and displays the light intensity and the angle between the axes of the polarizers. You can use the program’s built-in calculator to compare the relative intensity to the angle, the cosine of the angle, and the cosine
2
of the angle.
Equipment Setup
1. Mount the Basic Optics Light Source, Polarizer Holder, Polarizer Analyzer with Rotary Motion Sensor, and Aperture Bracket Holder with Light Sensor as shown. (Refer to the Intro­duction for more informa­tion.)
2. Connect the Light Sensor and Rotary Motion Sensor to the computer through a ScienceWorkshop or PASport interface (or inter­faces), and start DataStudio.
Light Sensor
Aperture Disk
Polarizers
Rotary Motion
Sensor
Light Source
Optics Bench
Figure 2: Equipment Setup
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012-09200A Polarization Analyzer
Experiment Setup
Select the Sensors and Set the Sample Rate
Refer to DataStudio on-line help for detailed information on selecting sensors and changing the sample rate.
1. Set up the Rotary Motion Sensor for high resolution (for example, 1440 Divisions per Rotation). Select Large Pulley (Groove) for the linear calibration (if you are using a PASport Sensor, this step is unecessary).
2. Set the sample rate of both sensors to 20 Hz, or 20 measurements per second.
Select the Display
Refer to DataStudio on-line help for detailed information selecting and changing displays.
1. Select a Graph display.
2. Set the axes of the Graph display so light intensity is on the vertical axis and angular position is on the horizon- tal axis.
Prepare to Record Data
Refer to DataStudio on-line help for detailed information on monitoring and recording data.
1. Turn both Polarizers so they are at the same beginning angle (e.g., zero degrees).
2. Start monitoring data.
3. Rotate one Polarizer back and forth until the transmitted light intensity is maximum.
4. Stop monitoring data.
Record Data
1. Start recording data.
2. Slowly rotate the Polarizer on the Polarization Analyzer in the clockwise direction. Continue to rotate the Po­larizer until you have made one complete rotation (360 degrees).
3. After one complete rotation, stop recording data.
Analyze the Data
Refer to the on-line help for DataStudio detailed information on creating and displaying calculations and using DataStudio for data analysis.
1. Use the Experiment Calculator in DataStudio software to create a calculation of the cosine of the angle between the Polarizers.
2
2. Repeat the procedure to create a calculation of the cosine
3. Use the Graph display to examine the plot of light intensity versus angle.
of the angle of the Polarizers.
4. Change the Graph display to show the plot of light intensity versus the cosine of the angle, and then change the
2
Graph display to show the plot of light intensity versus the cosine
5. Use Data Studio software to determine the relationship between the light intensity and the cosine
9
of the angle.
2
of the angle.
Polarization Analyzer 012-09200A
Questions
1. What is the shape of the plot of light intensity versus angle?
2. What is the shape of the plot of light intensity versus cosine of the angle?
3. What is the shape of the plot of light intensity versus cosine
2
of the angle?
4. Theoretically, what percentage of incident plane polarized light would be transmitted through three Polarizers which have their axes rotated 17 degrees (0.29 radians) from each other?Assume ideal polarizers and assume that the second polarizer’s axis is rotated 17 degrees (0.29 radians) from the first and that the third polarizer’s axis is rotated 17 degrees (0.29 radians) from the second.
5. From your data, determine the answer to Question #4 for the real polarizers.
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012-09200A Polarization Analyzer
Teacher’s Guide
Data Analysis
Sample Data
In the data analysis section, the curve fit for the polynomial function is
second degree. This indicates that the light
intensity varies as the square of the cosine of φ. This is confirmed by the curve fit for the linear function when light intensity is compared to the square of the cosine.
Answers to Questions
1. What is the shape of the graph of the intensity versus the angle?
Answers will vary. The shape of the graph of the intensity vs. the angle is approximately sinusoidal.
2. What is the shape of the graph of the intensity versus the cosine of the angle?
The shape of the graph of the intensity vs. the cosine of the angle is a parabola.
Sample Data: Light Intensity versus Angle
3. What is the shape of the graph of the intensity versus the square of the cosine of the angle?
The shape of the graph of the intensity vs. the square of the cosine of the angle is a straight line.
4. Theoretically, what percentage of incident plane polarized light would be transmitted through three polarizers which each have their axes rotated 17 degrees from each other? Assume ideal polarizers and assume that the first polarizer’s axis is 17 degrees from the axis of the second polarizer.
Assuming ideal filters, the intensity passing through the first filter would be 50% of the initial intensity. The intensity after the second filter would be reduced by
2
(17½) = 0.9145 of the intensity passing through the
cos first filter. Thus the intensity after passing through two filters would be 45.73%. The light passing through the third filter would be reduced by another 0.9145. So the three polarizers reduces the light intensity to 50%*(0.9145)2 = 41.82%.
5. From your graph, determine the answer to Question #4 for the real polarizers.
Answers will vary. From the example, we see that the intensity at 17½ is 98%, so the final intensity should be
2
= 96% of the intensity that passes through the first
(.98) filter. Using the sample data we see that only 33% passes through the first filter, thus the intensity of the light that passes through three filters is 96% of 33% or 31.68%.
11
Sample Data: Light Intensity vs. Cosine Angle
Sample Data: Light Intensity vs. Cosine2 Angle
Polarization Analyzer 012-09200A
Notes:
Technical Suppor t
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 (toll­free 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 can’t call PASCO right away, you won’t 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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