Experimental Physics

Principles and Practice for the Laboratory

Walter F. Smith, Walter F. Smith, Walter Fox Smith

• Publisher: CRC Press
• Year: 2020
• eBook ISBN: 9781498778800
• Topic: Biological Sciences
• Subtopic: Physics
• Index: Biological Sciences

This textbook provides the knowledge and skills needed for thorough understanding of the most important methods and ways of thinking in experimental physics. The reader learns to design, assemble, and debug apparatus, to use it to take meaningful data, and to think carefully about the story told by the data.

Key Features:

• Efficiently helps students grow into independent experimentalists through a combination of structured yet thought-provoking and challenging exercises, student-designed experiments, and guided but open-ended exploration.
• Provides solid coverage of fundamental background information, explained clearly for undergraduates, such as ground loops, optical alignment techniques, scientific communication, and data acquisition using LabVIEW, Python, or Arduino.
• Features carefully designed lab experiences to teach fundamentals, including analog electronics and low noise measurements, digital electronics, microcontrollers, FPGAs, computer interfacing, optics, vacuum techniques, and particle detection methods.
• Offers a broad range of advanced experiments for each major area of physics, from condensed matter to particle physics. Also provides clear guidance for student development of projects not included here.
• Provides a detailed Instructor's Manual for every lab, so that the instructor can confidently teach labs outside their own research area.

Part I

Fundamentals

1

Introduction

Walter Fox Smith

If (based on the poem by Rudyard Kipling)

If you can take your data, when all about you

Are losing theirs, and blaming it on you,

If you can trust your understanding, when others doubt you,

But make allowance for their doubting, too,

If you can persevere, and not give up,

And insist on good controls, when others say you’re wasting time,

Or think and plan instead of diving in,

And yet not plan too long, nor let your thinking stop your daring,

If you can dream, and not make dreams your master,

If you can theorize, and not make theories your aim,

If you can meet with defeat after defeat,

And keep on trying ‘till you find the reason,

If you can bear to hear the truth you’ve spoken

Questioned by referees who don’t know what they’re saying,

Or watch the apparatus you gave your life to broken,

And build it better than it was before,

If you scorn to publish tiny variations,

But striving for results that change the world,

Yet knowing almost always you will fail,

Not breathe a word about your disappointment,

If you can fill the lab with joy not bitterness,

And wordlessly remind your mates why they chose science,

And finish taking data when it’s boring,

Refusing to do other than your best,

If you can talk at conferences and fire the imagination,

Or walk through forests thinking of science,

If your collaborators know your virtue,

If journal editors value your review,

If you can read the manual and phone the expert,

If you can take a risk, and yet stay prudent,

Yours is the lab, and everything that’s in it,

And – which is more – you’ll be an experimentalist, my student!

Physics is an experimental science. That means that, although we greatly value the insights of theorists, the determination of whether a new idea is true or not is done experimentally. In addition to this important role of checking theories, experimentalists also often discover exciting, unexpected phenomena. (Unlike portrayals in the media, such discoveries are usually the result of carefully planned explorations and months or years of hard work.) In a third role, experimental physicists frequently make the first steps toward applying recent theoretical and experimental discoveries toward the creation of important new devices and technologies.

Even though experiments are so important, the vast majority of your physics time so far has been spent learning theory. This is partly because you need a solid understanding of fundamental theoretical ideas to design and interpret experiments. Nevertheless, since this may be the only full-credit course you take that’s devoted to experimental physics, it’s clearly the most important course you will ever take.

The experiments you’ll do are chosen carefully to allow you to learn efficiently. You will not be expanding humanity’s understanding of the universe, but the experiments will give you a genuine taste of the joys and frustrations of original research, and the experience should provide important guidance about careers you may wish to pursue.

You will improve your ability to understand a complicated undertaking at many levels, including theoretical background, planning, deep understanding of apparatus, optimal ways of connecting components, pilot testing, and rational debugging. It will require a great deal of patience and perseverance. You will likely need to change your approach, compared with earlier physics labs you’ve done. You will need to prepare more, focus more during the lab, be more ready to find outside resources in addition to the assigned reading, and think more deeply about your results.

If you put in the effort needed, you’ll find that this is one of the most rewarding and memorable courses of your career. What you learn will be essential in the research lab, but will also serve you well in areas from improving industrial processes to home repair. In fact, the ideas of debugging an apparatus and carrying out an experiment in the most efficient way can be applied to almost all areas of your life!

Note on Part II: Tools of an Experimentalist

It is absolutely essential that you complete the pre-lab reading before each lab in this section. If you don’t, you won’t be able to finish the lab in a timely fashion, you’ll understand little of what you’re supposed to, you’ll take more than your fair share of the instructor’s time, and you’ll have to stay later than the other students. It’s possible that in some previous lab courses you were able to make do without careful preparation; that approach truly will not work here.

You should expect to understand everything in the labs in this part fairly thoroughly, and you should get fairly close to the expected results, except when we tell you explicitly that something unexpected may happen. (Nevertheless, you’ll need to think hard!) If you complete a section of a lab and aren’t reasonably sure that you understand what’s going on, you should consult with a classmate or your instructor before proceeding to the next section.

Note on Part III: Fields of Physics

The labs in this part are designed to push you to become more independent as an experimentalist. You are expected to find related journal articles and relevant content in other textbooks. Much of the design of the experiment and the apparatus will be up to you. However, it’s smart to discuss your ideas with your instructor to avoid wasting time.

Walter Fox Smith is the Paul and Sally Bolgiano Professor of Physics at Haverford College. His research centers on self-assembling electronics. The eventual goal of this field is to start with several beakers of carefully chosen chemicals, and by mixing them in the appropriate sequence and applying appropriate stimuli (such as changing temperature or applying a voltage) cause the molecules to assemble into 10²³ identical circuits, with complex three-dimensional structures. Currently, the field’s focus is on understanding the principles that guide the self-assembly and the fundamental physics of charge transport through individual self-assembled circuit elements such as wires and transistors. Prof. Smith is also the author of “Waves and Oscillations: A Prelude to Quantum Mechanics” (Oxford University Press). He enjoys role-playing games, board and card games, jiu jitsu, and singing. He writes songs about physics and collects historical physics songs; you can find some of each at his website, PhysicsSongs.org (Figure 1.1).

FIGURE 1.1 Walter Fox Smith on a family trip to Belle Ile, France.

2

Planning and Carrying Out Experiments

Walter F. Smith

Contents

2.1 Literature Research

2.2 Reading Scientific Papers

2.3 Experimental Design

2.4 Modeling

2.5 Important Guidelines for Conducting Experiments

Preparation

Safety

Pilot Testing

Taking Data

2.6 Lab Notebooks

2.7 Troubleshooting

There’s a tremendous amount of work building the apparatus, getting the experiment to work. But sitting there late at night in the lab, and knowing light is going at bicycle speed, and that nobody in the history of mankind has ever been here before - that is mind-boggling. It’s worth everything.

– Lene Hau (physicist at Harvard who used a Bose-Einstein condensate to slow the speed of light to 17 m/s)

2.1 Literature Research

An essential part of science is understanding the state of your particular field of interest. What are the most important, well accepted fundamentals? What are the areas of current inquiry and controversy? What is possible experimentally with currently available instruments? Whether you are planning an experiment for research or conducting one of the more advanced experiments in this book, you should do some delving into journal articles (collectively referred to as “the literature”).

There are hundreds of research journals relating to physics. One of the most important for labs in this book is the American Journal of Physics, which focuses on instruction at the undergraduate level. Be...

Table of contents

• Cover
• Half-Title
• Title
• Copyright
• Contents
• Preface
• Acknowledgments
• Part I Fundamentals
• Part II Tools of an Experimentalist
• Part III Fields of Physics
• Index