PASCO OS-8500 User Manual

NORMALNORMAL

COMPONENTCOMPONENT

Includes

Teachers Notes

and

Typical

Experiment Results

Instruction Manual and

012-02744K

Experiment Guide for the PASCO scientific Model OS-8500

INTRODUCTORY OPTICS

SYSTEM

COMPONENT

NORMAL

COMPONENT

Introductory Optics System 012-02744K

012-02744K Introductory Optics System

Table of Contents

Section ..........................................................................................................Page

Preface to the Teacher ..................................................................................... iv

Introduction ...................................................................................................... 1

Equipment ........................................................................................................2

Setting Up the Equipment ................................................................................ 3

Copy Ready Experiments ................................................................................ 6

Basic Experiments

Experiment 1: Introduction to Ray Optics ................................................ 7

Experiment 2: The Law of Reflection ...................................................... 9

Experiment 3: Image Formation in a Plane Mirror .................................. 11

Experiment 4: The Law of Refraction ..................................................... 13

Experiment 5: Reversibility ..................................................................... 15

Experiment 6: Dispersion and Total Internal Reflection .......................... 17

Experiment 7: Converging Lens: Image and Object Relationships ......... 19

Experiment 8: Light and Color ................................................................ 21

Experiment 9: Two-Slit Interference ....................................................... 23

Experiment 10: Polarization ..................................................................... 25

Advanced Experiments

Experiment 11: Image Formation with Cylindrical Mirrors ...................... 27

Experiment 12: Image Formation with Spherical Mirrors ........................ 29

Experiment 13: Image Formation with Cylindrical Lenses ...................... 31

Experiment 14: Spherical Lenses—Spherical and Chromatic

Aberration, Aperture Size, and Depth of Field ............................. 33

Experiment 15: The Diffraction Grating .................................................. 35

Experiment 16: Single Slit Diffraction ..................................................... 37

Experiment 17: General Diffraction ......................................................... 39

Optical Instruments

Experiment 18: Introduction ..................................................................... 41

Experiment 19: The Projector .................................................................. 43

Experiment 20: The Magnifier ................................................................. 45

Experiment 21: The Telescope ................................................................. 47

Experiment 22: The Compound Microscope ........................................... 49

Appendix ........................................................................................................ 51

Replacement Parts ........................................................................................... 52

Teacher's Guide ........................................................................................... 52-67

Introductory Optics System 012-02744K

Please—Feel free to duplicate this manual subject to the copyright restrictions below.

The PASCO scientific Model OS-8500 Introductory Optics System manual is copyrighted and all rights reserved. However, permission is granted to nonprofit educational institutions for reproduction of any part of this 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 this 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. This 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 this product have to be returned to PASCO scientific, for whatever reason, notify PASCO scientific by letter or phone BEFORE returning the product. Upon notification, the return authorization and shipping instructions will be promptly issued.

➤➤

➤NOTE: NO EQUIPMENT WILL BE AC-

➤➤

CEPTED FOR RETURN WITHOUT AN AUTHORIZATION.

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 carton must be strong enough for the item

shipped.

➁ Make certain there is 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 box.

Address: PASCO scientific

10101 Foothills Blvd.

P.O. Box 619011

Credits

This manual authored by: Ed Pitkin

This manual edited by: Dave Griffith

Teacher's guide written by: Eric Ayars

Roseville, CA 95678-9011

Phone: (916) 786-3800

FAX: (916) 786-8905

012-02744K Introductory Optics System

Preface to the Teacher

The PASCO scientific Introductory Optics System is designed to provide a comprehensive introduction to laboratory optics. Of course, textbooks and lab books vary in the areas covered and the degree of complexity taught. To ensure that all essential concepts are covered, the experiments in this guide are based on material presented in several of the most comprehensive physics textbooks, including Modern Physics (Holt, Rinehart, and Winston) and PSSC Physics (Haber-Schaim, Dodge, and Walter). However, even if you do not use one of these textbooks, you should have little problem finding a collection of experiments in this manual that suits your needs.

The experiments are presented in three groups: Basic Experiments, Advanced Experiments, and Optical Instruments. All the experiments are designed as worksheets, to be copied from the manual for student use.

➤NOTE: Each experiment includes a series of questions with blank spaces for students to write their answers. We encourage students not to limit themselves to the space provided, but rather to use as much additional paper as needed to discuss, argue, prove points, etc.

The Advanced Experiments provide more in-depth investigations into some of the areas that were introduced in the Basic Experiments. These experiments are generally longer and more demanding. They should provide ample material for advanced classes and for independent study.

The Optical Instruments section provides an opportunity for students to apply some of the optics theory they have learned. Students can build and investigate a Projector, a Magnifier, a Microscope, and a Telescope. The optical bench and magnetic mounts make the setup easy.

In addition to the equipment provided in the PASCO Optics System, a few common items are needed for some experiments.

Additional Items Needed:

Items Purpose Expts

Pencil, Straightedge, Ray 1, 3, 5,

Protractor, White Paper Tracing 11, 13

Black Construction Circular 17

Paper, Pin Aperture

The Basic Experiments provide all the essentials for a solid introduction to optics.These experiments are designed to give clear presentations of the basic phenomena. The fill-in-the-blank format (used in all the experiments in this manual) provides a structured format and simple evaluation of student progress.

All experiments, except where otherwise stated, are best performed in a semi-darkened room. For optimal conditions, allow just enough light to enable comfortable reading of the lab book.

iii

Introductory Optics System 012-02744K

Notes

012-02744K Introductory Optics System

Introduction

A vast and complicated amount of information comes to us through our eyes. Because of this, the nature of light plays a critical role in our experience. Certainly our view of the world is colored (pun intended) by the nature of the medium which brings us so much information about it.

In our day to day life, we rarely concern ourselves with light, except perhaps when there is too much or not enough of it. We interact with light that has interacted with objects to determine such things as the color, shape, and position of the objects. We use this information to navigate, and to find what we want and what we wish to avoid. But our attention is almost always on the objects, not on the light that brings us the information.

In studying optics we change the focus of our attention. We still gain our information by interacting with light that has interacted with objects. But in studying optics we want to know what our observations tell us, not about the objects, but about light itself.

Before plunging into your experimental investigations of optics, its a good idea to become familiar with the equipment you will be using. The Equipment section of this manual will help you identify each of the components included with your optics system. The section entitled Equipment Setup gives some useful tips for aligning the optical equipment.

Introductory Optics System 012-02744K

Equipment

Figure one shows all the equipment that is included with your OS-8500 Introductory Optics System. The system also includes a fitted box, with cutouts for each component, and of course, this manual. If you wish to order additional components or replacement parts, please see the information at the end of the manual.

Incandescent Light Source

Optics Bench

Slit

Plate

Ray Optics

Mirror

Mask

Cylindrical

Lens

Slit

Parallel

Ray Lens

Crossed

Viewing

Screen

Arrow

Target

Ray Table Base

Ray Table

Ray Table Component Holder

Component Holders (3)

Lenses (3): 75, 150, and –150 mm focal lengths

Spherical Mirror: 50 mm focal length

DIFFRACTION GRATING

5276 LINES/cm

Color Filters:

Red

Green

Blue/Green

Virtual Image

Locators

(2)

Diffraction

Scale

Polarizers

(2)

Variable Aperture

Figure 1: Equipment Included in the OS-8500 Introductory Optics System

For Replacement Parts See Page 52

DIFFRACTION PLATE

A B C D E

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J I H G F DIFFRACTION PLATE

Diffraction Grating

Diffraction Plate

012-02744K Introductory Optics System

Setting Up the Equipment

Optics Bench

The Optics Bench is shown in Figure 2. The Light Source, Component Holders, and Ray Table Base all attach magnetically to the bench as shown. For proper optical alignment, the edge of each of these components should be mounted flush to the alignment rail, which is the raised edge that runs along one side of the bench.

Light Source

Alignment Rail

Ray Table

Component

Holder

Ray Table Base

Figure 2: Bench

NOTE: Avoid scratching or otherwise abusing the surface of the magnetic pads. If they get dirty, use only soapy water or rubbing alcohol for cleaning. Other solvents may dissolve the magnetic surface.

Switch

Notch Showing Location of

Filament

Figure 3: Using the Light Source

Filament Knob

Light Bulb

Incandescent Light Source

The Light Source is shown in Figure 3. To turn it on, connect the power cord to any grounded 105-125 VAC receptacle, and flip the switch on the top panel to ON. If at any time the light fails to come on, check with your instructor.

The Filament Knob on the top of the unit moves the light bulb from side to side. The notch at the bottom indicates the position of the light bulb filament, so that accurate measurements can be made during experiments.

Centering

Notch

Base Notch

Figure 4: Using the Component Holders

Component Holders and

(Top View)

Components

The Optics set comes with three regular Component Holders and one holder designed for use with the Ray Table. The regular Component Holders attach magnetically to the optics bench, as in Figure 4. The notch at the top of each holder is for centering components on the holder. The notches in the base of the holders are for accurate distance measurements on the metric scale of the bench. These base notches—and also the edge of the component holder base—are positioned so that they align with the vertical axis of a mounted lens or mirror. Accurate measurements of component position can be made as shown in Figure 5.

0 1 2 3 4 5

Vertical Axes of Lens or Mirror

Figure 5: Component

Alignment

Introductory Optics System 012-02744K

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DIFFRACTION PLATE

A B C D E

DIFFRACTION PLATE

J I H G F

Variable Aperture

Polarizer

Lens or Mirror

Figure 6: Using the Component Holders

The Variable Aperture, the Polarizers, and the Lenses attach to the component

Concave Side

Convex Side

holders as shown in Figure 6. Use the centering notch to align the components along the optical axis of the bench and, in the case of the Polarizers, to measure the angle of polarization.

The Spherical Mirror mounts onto the component holders in

Figure 7:

The Spherical Mirror

the same manner as the Lenses. However, the mirror is silvered on both sides, so that, depending on which side you use, it can be a convex or a concave mirror (see Figure 7).

Diffraction Experiments

Set up diffraction experiments as shown in Figure 8. You can use either the Diffraction Plate, which has ten different apertures, or the Diffraction Grating, which has a line spacing of 600 lines/mm. If you are using the Diffraction Plate, place the Slit Mask on the other side of the

Slit Spacing

center-to-center

(mm)

Pattern No. Slits

Slit Width

(mm)

A 1 0.04

B 1 0.08

C 1 0.16

D 2 0.04 0.125

E 2 0.04 0.250

F 2 0.08 0.250

G 10 0.06 0.250

H 2 (crossed) 0.04

I 225 Random Circular Apertures (.06 mm dia.)

J 15 x 15 Array of Circular Apertures (.06 mm dia.)

Figure 9: Diffraction Plate Apertures

component holder and position it so that only a single diffraction aperture is illuminated by the light from the light source.

When you look through the aperture or grating toward the light source, you will see the diffraction pattern superimposed over the Diffraction Scale. You can use the illuminated scale to accurately measure the geometry of the diffraction pattern. Information about analyzing the measurements is provided in experiments 9, 15, 16, and

17. The dimensions of the apertures in the Diffraction Plate are provided in Figure 9.

Ray Table Base

Diffraction Scale

Diffraction Plate or

Diffraction Grating

Figure 8: Setting Up a Diffraction Experiment

Slit Mask: to isolate a

single diffraction aper-

ture (not needed when

using the Diffraction

Grating)

Look through

IFFRACTION PLATE

A B C D E

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.. .

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DIFFRACTION PLATE

. . . .

. .

. . . .

J I H G F

here toward

Diffraction

Scale to view (and measure) the diffraction

pattern.

012-02744K Introductory Optics System

Basic Ray Optics Setup

The basic setup for Ray Optics is shown in Figure 10. The Ray Table Base should be flush against the alignment rail. The Ray Table fits over the pin on the top of the Base.

Component Holder

Ray Table and Base

Figure 10: Basic Ray Optics Setup

Notice that the Ray Table Base is slightly slanted. When mounting the base on the Optics Bench, be sure the Ray Table slants down toward the Light Source. This ensures sharp, bright rays. (In all the experiments described in this manual, the error introduced by this tilt is negligible.)

Ray Table

Component Holder

Viewing

Screen

Slit Plate

➀ the lateral position of the Slit Plate on its Component

Holder,

➁ the position of the light source filament with respect to

the optical axis, and

➂ the rotation of the Ray Table.

To align a single ray:

4. Use the Slit Mask to block all but the desired ray.

2. Adjust the position of the filament.

Figure 11: Single Ray Setup

1. Adjust the lateral position of the Slit Plate.

3. Adjust the rotation angle of the Ray Table.

Either side of the Ray Table may be used. One side has a rotational scale, the other has both a rotational scale and a grid that may be used for linear measurements.

The Slit Plate is attached to a component holder between the Light Source and the Ray Table. The positioning shown in the illustration will give clear, sharp rays in a slightly darkened room. However, the quality of the rays is easily varied by adjusting the distance between the Light Source and the Slit Plate. Narrower, less divergent rays may be obtained by sliding the Light Source farther away from the slits, but there is a corresponding loss of brightness.

The Ray Table Component Holder attaches magnetically to the Ray Table as shown. It may be used to mount the Viewing Screen, the Polarizer, or another component.

Single Ray Setup

Most quantitative ray optics experiments are most easily performed using a single ray. This can be obtained by using the Slit Mask, as shown in Figure 11, to block all but the desired ray.

For accurate measurements using the rotational scale, the incident ray must pass directly through the center of the Ray Table. To accomplish this, alternately adjust:

When one of the rays is aligned in this manner, place the Slit Mask on the other side of the Component Holder to block all but the desired ray.

Parallel Ray Setup

Parallel rays are obtained by positioning the Parallel Ray Lens between the Light Source and the slits, as shown in Figure 12. Use the parallel lines of the Ray Table grid as a reference, and adjust the longitudinal position of the lens until the rays are parallel.

Parallel Ray Lens

Slit Plate

Figure 12: Single Ray Setup

Introductory Optics System 012-02744K

Copy Ready Experiments

The following experiments are written in worksheet form.

Feel free to photocopy them for use in your lab.

➤NOTE: The first paragraph in each experiment lists all the equipment

needed to perform the experiment. Be sure to read this equipment list first, as

the requirements vary with each experiment.

012-02744K Introductory Optics System

Experiment 1: Introduction to Ray Optics

EQUIPMENT NEEDED:

-Optics Bench, -Light Source,

-Ray Table and Base, -Component Holder,

-Slit Plate, -Ray Table Component Holder,

-Viewing Screen.

Purpose

➀ Observe straight line propagation of light. ➁ Use Ray Tracing to locate an object.

Procedure

Set up the equipment as shown in Figure 1.1, and turn on the Light Source. Darken the room enough so the light rays on the Ray Table are easily visible.

Straight Line Propagation of Light

Observe the light rays on the Ray Table.

Slit Plate

Figure 1.1 Equipment Setup

Viewing Screen

➀ Are the rays straight? _______________________________________________________. ➁ How does the width and distinctness of each ray vary with its distance from the Slit Plate?

_________________________________________________________________________. Set the Viewing Screen and its holder aside for the next step.

➂ Lower your head until you can look along one of the "Rays" of light on the Ray Table. Where does

the light originate? What path did it take going from there to your eye? Try this for several rays. _____________________________________________________________________.

Replace the Viewing Screen as shown in Figure 1.1. Rotate the Slit Plate slowly on the component holder until the slits are horizontal. Observe the slit images on the Viewing Screen.

➃ How does the width and distinctness of the slit images depend on the angle of the Slit Plate?

_________________________________________________________________________.

➄ For what angle of the Slit Plate are the images most distinct? For what angle are the images least

distinct?_________________________________________________________________.

Introductory Optics System 012-02744K

➅ On a separate sheet of paper, explain your observations in terms of the straight line propaga-

tion of light. Include a diagram showing how the width of the slit images depends on the orientation of the Light Bulb filament with respect to the Slit Plate. ____________________________________________________________________________________________.

Ray Tracing: Locating the Filament

Filament

Light Source

Note: The vertical edge of the notch on the side of the Light Source indicates the position of the filament.

Component

Holder

Figure 1.2: Ray Tracing

Slit Plate

Center

You can use the fact that light propagates in a straight line to measure the distance between the Light Source filament and the center of the Ray Table. Figure 1.2 shows how. The rays on the Ray Table all originate from the filament of the Light Source. Since light travels in a straight line, you need only extend the rays backward to locate the filament. (See Step 3 in the first part of this experiment.)

Rays on Ray

Table

Paper

Place a piece of blank white paper on top of the Ray Table, holding it there with a piece of tape. Make a reference mark on the paper at the position of the center of the Ray Table. Using a pencil and straight edge, trace the edges of several of the rays onto the paper.

Remove the paper. Use the pencil and straightedge to extend each of the rays. Trace them back to their common point of intersection. (You may need to tape on an additional sheet of paper.) Label the filament and the center of the Ray Table on your diagram.

➀ Measure the distance between your reference mark and the point of intersection of the rays.

_______________________________________________________________________.

➁ Use the metric scale on the Optics Bench to measure the distance between the filament and

the center of the Ray Table directly (see the note in Figure 1.2). _____________________________________________________________________________________________.

➂ How well do your measurements in Steps 1 and 2 agree? Comment.

________________________________________________________________________________________. One of the key ideas that this experiment illustrates is the ability for us to trace light rays to

their origin or apparent origin. This concept will prove most useful in future experiments.

012-02744K Introductory Optics System

NORMALNORMAL

COMPONENTCOMPONENT

Experiment 2: The Law of Reflection

EQUIPMENT NEEDED:

-Optics Bench -Light Source

-Ray Table and Base -Component Holder

-Slit Plate -Slit Mask

-Ray Optics Mirror.

Slit Mask

COMPONENTCOMPONENT

NORMALNORMAL

Slit Plate

Introduction

The shape and location of the image created by reflection from a mirror of any shape is determined by just a few simple principles. One of these principles you already know: light propagates in a straight line. You will have an opportunity to learn the remaining principles in this experiment.

To determine the basic principles underlying any phenomenon, it is best to observe that phenomenon in its simplest possible form. In this experiment, you will observe the reflection of a single ray of light from a plane mirror. The principles you discover will be applied, in later experiments, to more complicated examples of reflection.

Figure 2.1 Equipment Setup

Angle of

Reflection

Angle of

Incidence

Figure 2.2 Incident and Reflected Rays

Introductory Optics System 012-02744K

Procedure

Set up the equipment as shown in Figure 2.1. Adjust the components so a single ray of light is aligned with the bold arrow labeled “Normal” on the Ray Table Degree Scale. Carefully align the flat reflecting surface of the mirror with the bold line labeled “Component” on the Ray Table. With the mirror properly aligned, the bold arrow on the Ray Table is normal (at right angles) to the plane of the reflecting surface.

Rotate the Ray Table and observe the light ray. The angles of incidence and reflection are measured with respect to the normal to the reflecting surface, as shown in Figure 2.2.

By rotating the Ray Table, set the angle of incidence to each of the settings shown in Table

2.1. For each angle of incidence, record the angle of reflection (Reflection measurements with the incident ray coming from the opposite side of the normal (Reflec-

tion

➀ Are the results for the two trials the same? If not, to what do you attribute the differences?

________________________________________________________________________

➁ Part of the law of reflection states that the incident ray, the normal and the reflected ray all lie

in the same plane. Discuss how this is shown in your experiment _____________________________________________________________________________________________.

). Repeat your

➂ What relationship holds between the angle of incidence and the angle of reflection?

______________________________________________________________________________

Additional Questions

➀ The Law of Reflection has two parts. State both

parts.

➁ You were asked to measure the angle of reflection

when the ray was incident on either side of the normal to the surface of the mirror. What advantages does this provide?

➂ Physicists expend a great deal of energy in attempts

to increase the accuracy with which an exact law can be proven valid. How might you test the Law of Reflection to a higher level of accuracy than in the experiment you just performed?

Angle of: Incidence Reflection1 Reflection

Table 2.1 Data

0°

10°

20°

30°

40°

50°

60°

70°

80°

90°

012-02744K Introductory Optics System

Experiment 3: Image Formation in a Plane Mirror

EQUIPMENT NEEDED:

-Optics Bench -Light Source

-Ray Table and Base -Component Holder

-Slit Plate -Ray Optics Mirror

Paper

Introduction

Figure 3.1 Equipment Setup

Looking into a mirror and seeing a nearly exact image of yourself hardly seems like the result of simple physical principles. But it is. The nature of the image you see in a mirror is understandable in terms of the principles you have already learned: the Law of Reflection and the straight-line propagation of light.

In this experiment you will investigate how the apparent location of an image reflected from a plane mirror relates to the location of the object, and how this relationship is a direct result of the basic principles you have already studied.

Procedure

Set up the equipment as shown in Figure 3.1. Adjust the Slit Plate and Light Source positions for sharp, easily visible rays.

As shown, place a blank, white sheet of paper on top of the Ray Table, and place the Ray Optics Mirror on top of the paper. Position the mirror so that all of the light rays are reflected from its flat surface. Draw a line on the paper to mark the position of the flat surface of the mirror.

Look into the mirror along the line of the reflected rays so that you can see the image of the Slit Plate and, through the slits, the filament of the Light Source. (Rotate the mirror as needed to do this.)

➀ Do the rays seem to follow a straight line into the mirror? ________________________________.

With a pencil, mark two points along one edge of each of the incident and reflected rays. Label the points (r etc.), so you know which points belong to which ray.

1,r2

Remove the paper and reconstruct the rays as shown on the next page (Figure 3.2), using a pencil and straightedge. If you need to, tape on additional pieces of paper. Draw dotted lines to extend the incident and reflected rays. (If this ray tracing technique is unfamiliar to you, review ray tracing in Experiment 1: Introduction to Ray Optics.)

On your drawing, label the position of the filament and the apparent position of its reflected image.

Introductory Optics System 012-02744K

Image of the

Filament

90˚

Filament

Figure 3.2 Ray Tracing

➁ What is the perpendicular distance from the filament to the plane of the mirror (distance d1, as shown in the

Figure 3.2)? ________________________________________________.

➂ What is the perpendicular distance from the image of the filament to the plane of the mirror (distance d

, as

shown in the Figure)? _________________________________________. Change the position of the mirror and the Light Source and repeat the experiment.

➃ What is the relationship between object and image location for reflection in a plane mirror?

________________________________________________________________________.

Additional Questions

➀ If one wall of a room consists of a large, flat mirror, how much larger does the room appear to be than it

actually is?

➁ Make a diagram illustrating why an image of the letter F, reflected from a plane mirror, is inverted. (Treat

each corner on the F as a source of light. Locate the image for each source to construct the image of the F.)

➂ How does the size of the image reflected from a plane mirror relate to the size of the object?

012-02744K Introductory Optics System

NORM

NORMAL

Experiment 4: The Law of Refraction

EQUIPMENT NEEDED:

-Optics Bench -Light Source

-Ray Table and Base -Component Holder

-Slit Plate -Slit Mask

-Cylindrical Lens.

Slit Mask

Angle of

Incidence

Introduction

As you have seen, the direction of light propagation changes abruptly when light encounters a reflective surface. The direction also changes abruptly when light passes across a boundary between two different media of propagation, such as between air and acrylic, or between glass and water. In this case, the change of direction is called Refraction.

As for reflection, a simple law characterizes the behavior of a refracted ray of light. According to the Law of Refraction, also known as Snell’s Law:

The quantities n1 and n2 are constants, called indices of refraction, that depend on the two media through which the light is passing. The angles θ1 and θ2 are the angles that the ray of light makes with the normal to the boundary between the two media (see the inset in Figure 4.1). In this experiment you will test the validity of this law, and also measure the index of refraction for acrylic.

Slit Plate

Figure 4.1 Equipment Setup

sin θ1 = n2 sin θ

Angle of

Refraction

Procedure

Set up the equipment as shown in Figure 4.1. Adjust the components so a single ray of light passes directly through the center of the Ray Table Degree Scale. Align the flat surface of the Cylindrical Lens with the line labeled “Component”. With the lens properly aligned, the radial lines extending from the center of the Degree Scale will all be perpendicular to the circular surface of the lens.

Introductory Optics System 012-02744K

Without disturbing the alignment of the Lens, rotate the Ray Table and observe the refracted ray for various angles of incidence.

➀ Is the ray bent when it passes into the lens perpen-

dicular to the flat surface of the lens? _______________________________________

_______________________________________.

➁ Is the ray bent when it passes out of the lens

perpendicular to the curved surface of the lens? _______________________________________

_______________________________________. By rotating the Ray Table, set the angle of inci-

dence to each of the settings shown in Table 4.1 on the following page. For each angle of incidence, measure the angle of refraction (Refraction

Repeat the measurement with the incident ray striking from the opposite side of the normal (Refraction2).

Angle of: Incidence Refraction1Refraction

0°

10°

20°

30°

40°

50°

60°

70°

80°

90°

➂ Are your results for the two sets of measurements

Table 4.1 Data

the same? If not, to what do you attribute the differences? ___________________________________________________________________

_______________________________________________________________________. On a separate sheet of paper, construct a graph with sin(angle of refraction) on the x-axis

and sin(angle of incidence) on the y-axis. Draw the best fit straight line for each of your two sets of data.

➃ Is your graph consistent with the Law of Refraction? Explain.

_____________________________________________________________________________________________.

➄ Measure the slope of your best fit lines. Take the average of your results to determine the

index of refraction for acrylic (assume that the index of refraction for air is equal to 1.0). n = ________________________________________.

Additional Questions

➀ In performing the experiment, what difficulties did you encounter in measuring the angle of

refraction for large angles of incidence?

➁ Was all the light of the ray refracted? Was some reflected? How might you have used the

Law of Reflection to test the alignment of the Cylindrical Lens?

➂ How does averaging the results of measurements taken with the incident ray striking from

either side of the normal improve the accuracy of the results?

012-02744K Introductory Optics System

Experiment 5: Reversibility

Equipment Needed:

-Optics Bench -Light Source

-Ray Table and Base -Component Holder

-Slit Plate -Slit Mask

-Cylindrical Lens.

Introduction

In Experiment 4, you determined the relationship that exists between the angle of incidence and the angle of refraction for light passing from air into a more optically dense medium (the Cylindrical Lens). An important question remains. Does the same relationship hold between the angles of incidence and refraction for light passing out of a more optically dense medium back into air? That is to say, if the light is traveling in the opposite direction, is the law of refraction the same or different? In this experiment, you will find the answer to this question.

Procedure

Set up the equipment as shown in Figure 5.1. Adjust the components so a single ray of light passes directly through the center of the Ray Table Degree Scale. Align the flat surface of the Cylindrical Lens with the line labeled “Component”. With the lens properly aligned, the radial lines extending from the center of the Degree Scale will all be perpendicular to the circular surface of the lens.

Slit Mask

Incidence

Slit Plate

0 3

Figure 5.1 Equipment Setup

Internal Angle

of Incidence

(Incidence

)

Figure 5.2 Internal Angle of Incidence

0 4

T N

N O P

M O C

T N E

O P M

O C

NORMAL

COMPONENT

4 0

3 0

COMPONENT

NORMAL

Refraction

(Refraction

)

Angle of

Refraction

Without disturbing the alignment of the lens, rotate the Ray Table and set the angle of incidence to the values listed in Table 5.1 on the following page. Enter the corresponding angles of Refraction in the table in

two columns: Refraction1 and Incidence2. (Let Incidence2 = Refraction1).

Introductory Optics System 012-02744K

Table 5.1 Data

Ray Incident on: Flat Surface Curved Surface

Angle of: Incidence

Refraction

Incidence

Refraction

0°

10°

20°

30°

40°

50°

60°

70°

80°

90°

Now let the incident ray strike the curved surface of the lens. (Just rotate the Ray Table 180°.) The internal angle of incidence for the flat surface of the Cylindrical Lens is shown in Figure 5.2. Set this angle of incidence to the values you have already listed in the table (Incidence2). Record the corresponding angles of refraction (Refraction2).

➀ Using your collected values for Incidence

and Refraction1, determine the index of refraction for

the acrylic from which the Cylindrical Lens is made. (As in experiment 4, assume that the index of refraction for air is equal to 1.0.)

______________________________________________________________________.

➁ Using your collected values for Incidence

and Refraction2, redetermine the index of refraction

for the acrylic from which the Cylindrical Lens is made. n

______________________________________________________________________.

➂ Is the Law of Refraction the same for light rays going in either direction between the two

media? ____________________________________________________________________.

➃ On a separate sheet of paper, make a diagram showing a light ray passing into and out of the

Cylindrical Lens. Show the correct angles of incidence and refraction at both surfaces traversed by the ray. Use arrow heads to indicate the direction of propagation of the ray. Now reverse the arrows on the light ray. Show that the new angles of incidence and refraction are still consistent with the Law of Refraction. This is the principle of optical reversibility.

➄ Does the principle of optical reversibility hold for Reflection as well as Refraction? Explain.

_________________________________________________________________________.

012-02744K Introductory Optics System

Experiment 6: Dispersion and Total Internal Reflection

EQUIPMENT NEEDED:

-Optics Bench -Light Source

-Ray Plate and Base -Component Holder

-Slit Plate -Slit Mask

-Cylindrical Lens -Ray Table Component Holder

-Viewing Screen.

COMPONENT

Viewing

Screen

Angle of

Incidence

Figure 6.1 Equipment Setup

Introduction

In this experiment you will look at two phenomena related to refraction: Dispersion and Total Internal Reflection. Dispersion introduces a complication to the Law of Refraction, which is that most materials have different indexes of refraction for different colors of light. In Total Internal Reflection, it is found that in certain circumstances, light striking an interface between two transparent media can not pass through the interface.

Procedure

Set up the equipment as shown in Figure 6.1, so a single light ray is incident on the curved surface of the Cylindrical Lens.

Dispersion

Set the Ray Table so the angle of incidence of the ray striking the flat surface of the lens (from inside the lens) is zero-degrees. Adjust the Ray Table Component Holder so the refracted ray is visible on the Viewing Screen.

Slowly increase the angle of incidence. As you do, watch the refracted ray on the Viewing Screen.

➀ At what angle of refraction do you begin to notice color separation in the refracted ray?

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