PASCO WA-9316A User Manual

Experiment Guide

See the PASCO Web site at www.pasco.com for information about the Complete Microwave Optics System.

013-13906B

Complete Microwave Optics System

WA-9316A

Experiment Guide

Important Note

• CAUTION — Under some circumstances, microwaves can interfere with electronic medical devices. If you use a pacemaker, or other electronic medical device, check with your doctor or the manufacturer to be certain that low power microwaves at a frequency of 10.525 GHz will not interfere with its operation.

Experiment Guide

Table Of Contents

Introduction - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3

Microwave Optics System Equipment - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3

Technical Support - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4

Experiments

Experiment 1: Introduction to the Microwave Optics System- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5

Experiment 2: Reflection - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 9

Experiment 3: Standing Waves - Measuring Wavelengths - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -11

Experiment 4: Refraction Through a Prism - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -15

Experiment 5: Polarization - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -17

Experiment 6: Double-Slit Interference - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -19

Experiment 7: Lloyds Mirror - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -21

Experiment 8: Fabry-Perot Interferometer - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -23

Experiment 9: Michelson Interferometer - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -25

Experiment 10: Fiber Optics- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -27

Experiment 11: Brewster’s Angle - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 28

Experiment 12: Bragg Diffraction - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -31

(Note that Experiment 3 can be done with the WA-9319A Microwave Detector Probe and that Experiment 11 and Experiment 12 use equipment from the WA-9315 Microwave Accessory Package.)

Teacher’s Guide - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -33

013-13906B Introduction

Holder

Arm

Introduction

The experiments are designed to give a thorough introduction to wave theory using the Microwave Optics System. Basic principles are only briefly discussed in each experiment because it is assumed that the students have the appropriate theoretical background. These experiments range from quantitative investigation of reflection and refraction to microwave models of the Michelson and Fabry-Perot interferometers. Experiments for investigating Bragg diffraction and Brewster’s angle are included, but require the Microwave Accessory Package.

The experiments are written in a worksheet format. Fee free to copy the experiment write-ups for use in your lab.

Microwave Optics System Equipment

The Complete Microwave Optics System consists of the Microwave Optics System (WA-9314C) and the Microwave Accessory Package (WA-9315). The Microwave Optics System comes with a 2.85 centimeter wavelength microwave transmitter and a receiver with variable amplification from 1X to 30X. All the accessory equipment needed to investigate a variety of wave phenomena is also included.

Microwave Optics System (WA-9314C) Microwave Optics System (WA-9314C)

Microwave Receiver WA-9800 Metal Reflectors (2)

Microwave Transmitter WA-9801 Partial Reflectors (2)

Mounting Stands (2) WA-9802 Polarizers (2)

Power Adapters (2) Slit Extender Arm

Goniometer Narrow Slit Spacer

Fixed Arm Assembly Wide Slit Spacer

Rotating Table Ethafoam Prism Mold

Component Holders (2) Styrene Pellets (1 jar)

Rotating Component Holder Tubular Plastic Bags (4)

Microwave Accessory Package (WA-9315)

Cubic Lattice* (Bragg’s crystal model)

Polyethylene Panel

*The Cubic Lattice contains 100 metal spheres in a 5 by 5 by 4 array.

Assembling Equipment for Experiments

The arms of the Goniometer or the Fixed Arm Assembly slide through the holes in the Component Holders as shown. Make sure the magnetic strip on the bottom of the arm grips the base of the carriage. To adjust the position of the holders, just slide them along the arms. Attach the mounting stands of the microwave Transmitter and Receiver to the arms of the Goniometer or Fixed Arm Assembly in the same manner.

For most experiments it is advantageous to attach the Transmitter to the long arm of the Goniometer and the Receiver to the shorter, rotatable arm. This maintains a fixed relationship between the microwave beam and components mounted on the long arm (or on the degree plate) of the Goniometer. In turn the Receiver moves easily to sample the output.

Experiment Guide Technical Support

Reflectors, Partial Reflectors, Polarizers, Slit Spacers, and the Slit Extender Arm all attach magnetically to the Component Holders. The metric scale along the Goniometer and Fixed Arm Assembly arms and the degree plate at the junction of the Goniometer arms allow easy measurement of component placement.

• It is recommended that the apparatus be mounted on a CLEAN, SMOOTH table.

• Before setting up the equipment, brush off any material—particularly metal chips—that might have adhered to the magnetic strips and magnetic pads.

Maintenance

Regular maintenance for this equipment is minimal. When not in use, the equipment can be stored in the shipping box. Inspect the magnetic strips and magnetic pads and remove anything - especially bits of metal - that adhere to them.

If problems arise with the equipment DO NOT attempt to fix this equipment yourself. Contact PASCO scientific. (See the Technical Support information.)

Technical Support

For assistance with any PASCO product, contact PASCO at:

Address: PASCO scientific

10101 Foothills Blvd. Roseville, CA 95747-7100

Phone: +1 916 786 3800 (worldwide)

800-772-8700 (U.S.)

E-mail: support@pasco.com

Web www.pasco.com

For the latest information about the Complete Microwave Optics System or its accessories,

go to the PASCO web site at www.pasco.com and enter the model number or the product name in the search window.

Limited Warranty For a description of the product warranty, see the PASCO catalog. Copyright The PASCO scientific Experiment Guide is copyrighted with all rights reserved. Permission is granted to non-profit educational institutions for reproduction of any part of this manual, providing the reproductions are used only in their laboratories and classrooms, and are not sold for profit. Reproduction under any other circumstances, without the written consent of PASCO scientific, is prohibited. Trademarks PASCO, PASCO Capstone, PASPORT, SPARK Science Learning System, SPARK SLS, and SPARKvue are trademarks or registered trademarks of PASCO scientific, in the United States and/or in other countries. For more information visit www.pasco.com/legal.

Product End of Life Disposal Instructions:

This electronic product is subject to disposal and recycling regulations that vary by country and region. It is your responsibility to recycle your electronic equipment per your local environmental laws and regulations to ensure that it will be recycled in a manner that protects human health and the environment. To find out where you can drop off your waste equipment for recycling, please contact your local waste recycle/disposal service, or the place where you purchased the product.

The European Union WEEE (Waste Electronic and Electrical Equipment) symbol (to the right) and on the product or its packaging indicates that this product must not be disposed of in a standard waste container.

013-13906B Experiment 1: Introduction to the Microwave Optics System

Figure1.1: Equipment Setup

Effective Point of Emission of

Transmitter Signal

Effective Point of Reception

of Transmitter Signal

5 cm

Figure1.2: Equipment Setup

Experiment 1: Introduction to the Microwave Optics System

Equipment Needed:

Item Item

Transmitter Goniometer

Receiver Reflector

Purpose

This activity gives an introduction to the Microwave Optics System which may prove helpful in learning to use the equipment effectively and in understanding the significance of measurements made with this equipment.

Procedure

1. Arrange the Transmitter and Receiver on the Goniometer as shown in Figure 1 with the Transmitter attached to the fixed arm. Be sure to adjust both Transmitter and Receiver to the same polarity — the horns should have the same orientation, as shown.

2. Plug in the Transmitter and the Receiver. Turn the INTENSITY selection switch on the Receiver from OFF to 10X. (The LEDs should light up on both units.)

3. Adjust the Transmitter and Receiver so the distance between the source diode in the Transmitter and the detector diode in the Receiver (the distance labeled R in Figure 1) is 40 cm (see Figure 1.2 for location of points of transmission and reception). The diodes are at the locations directly above the points marked “T” and “R” on the stands. Adjust the INTENSITY and VARIABLE SENSITIVITY knobs on the Receiver so that the meter reads

1.0 (full scale).

4. Set the distance R to each of the values shown in Table 1. Record the meter reading for each value of R. (Do not adjust the Receiver controls between measurements.) After making the measurements, perform the calculations shown in the table.

Table 1.1: Data

R (cm) Meter Reading (M) M X R (cm)

M X R

(cm2)

100

Experiment Guide Experiment 1: Introduction to the Microwave Optics System

Reflector

Figure1.3: Reflections

IMPORTANT: Reflections from nearby objects, including the table top, can affect the results of your microwave experiments. To reduce the effects of extraneous reflections, keep your experiment table clear of all objects, especially metal objects, other than those components required for the current experiment.

Figure1.4: Polarization

Figure1.5: Signal Distribution

Angle = 180°

5. Set R to some value between 70 and 90 cm. While watching the meter, slowly decrease the distance between the Transmitter and Receiver. Does the meter deflection increase steadily as the distance decreases?

6. Set R to between 50 and 90 cm. Move a Reflector, its plane parallel to the axis of the microwave beam, toward and away from the beam axis, as shown in Figure

1.3. Observe the meter readings. Can you explain your observations in steps 5 and 6? (Don’t worry if you can’t; you will have a chance to investigate these phenomena more closely in other experiments.) For now just be aware of the following:

7. Loosen the hand screw on the back of the Receiver and rotate the Receiver as shown in Figure 1.4. This varies the polarity of maximum detection. (Look into the receiver horn and notice the alignment of the detector diode.) Observe the meter readings through a full 360 degree rotation of the horn. A small mirror may be helpful to view the meter reading as the receiver is turned. At what polarity does the Receiver detect no signal?

NOTE: Try rotating the Transmitter horn as well. When finished, reset the Transmitter and Receiver so their polarities match (e.g., both horns are horizontal or both horns are vertical).

8. Position the Transmitter so the output surface of the horn is centered directly over the center of the Degree Plate of the Goniometer arm (see Figure 1.5). With the Receiver directly facing the Transmitter and as far back on the Goniometer arm as possible, adjust the Receiver controls for a meter reading of 1.0. Then rotate the rotatable arm of the Goniometer as shown in the figure. Set the angle of rotation (measured relative to the 180-degree point on the degree scale) to each of the values shown in Table 2, and record the meter reading at each setting

Table 1.2: Data

Angle of Receiver

Meter

Reading

Angle of

Receiver

Meter

Reading

Angle of

Receiver

Meter

Reading

90° 160 230

100 170 240

110 180 250

120 190 260

130 200 270

140 210

150 220

013-13906B Experiment 1: Introduction to the Microwave Optics System

Questions

1. The electric field of an electromagnetic wave is inversely proportional to the distance from the wave source, (i.e.,  E = 1/R). Use your data from step 4 of the experiment to determine if the meter reading of the Receiver is directly proportional to the electric field of the wave.

2. The intensity of an electromagnetic wave is inversely proportional to the square of the distance from the wave source (i.e.,

3. Considering your results in step 7, to what extent can the Transmitter output be considered a spherical wave? A plane

I = 1/R tional to the intensity of the wave.

wave?

). Use your data from step 4 of the experiment to determine if the meter reading of the Receiver is directly propor-

Experiment Guide Experiment 1: Introduction to the Microwave Optics System

013-13906B Experiment 2: Reflection

Figure 2.1: Equipment Setup

Figure 2.2: Angles of Incidence and Reflection