Course Meeting Times
Labs: 2 sessions / week, 3 hours / session
The purposes of Junior Lab are to give you hands-on experience with some of the experimental basis of modern physics and, in the process, to deepen your understanding of the relations between experiment and theory, mostly in atomic and nuclear physics. You will do experiments on phenomena whose discoveries led to major advances in physics. The data you obtain will have the inevitable systematic and random errors that obscure the relations between the macroscopic observables of our sensory experience and the ideal laws that govern the submicroscopic world of atoms and nuclei. You will be challenged to learn how each of the experimental setups works, to master its manipulation so that you obtain the best possible data, and then to interpret the data in light of theory and a quantitative assessment of the errors. We think you will find satisfaction in observing, measuring and understanding phenomena many of which would have won you the Nobel Prize if you had discovered them.
You are expected to work in pairs, sharing as evenly as possible in the measurements, the analysis and the interpretation of the data. The best choice for a lab partner may be someone who lives nearby and has a schedule that matches yours so you can get together outside of class to analyze and interpret your results. Most students find they require at least 18 hours per week to do the work of the course.
During the Fall term, the first two sessions familiarize you with the lab giving everyone a common foundation in experimental techniques, data analysis and computing tools, including MATLAB® and LaTex. One 3 hour session is scheduled for two short introductory experiments: one of which must be 'Poisson Statistics' while the other may either be 'Transmission of Electromagnetic Pulses' or 'The Photoelectric Effect'. The preparatory questions (in the lab guides) and one written summary resulting from these preliminary experiments will be graded (to let you know how you're doing) but not recorded, so your final grade will be unaffected. Following this introductory period, students will plan and execute four longer experiments. The first will be executed in 5 sessions, while the last three will be done in 4 sessions each. The term culminates in a week-long series of public oral presentations given by students to peers, friends, and faculty in an American Physical Society conference type event.
During the Spring term, the first class period is dedicated to selecting partners and brief introductory notes by section instructors. Students will select 4 different experiments, each of which will require 5 separate lab sessions. The experiments from which you may choose include:
- The Zeeman effect
- Optical pumping (2 setups available)
- Pulsed NMR
- Mössbauer spectroscopy (2 setups available)
- Doppler-free spectroscopy
- Quantum information processing (requires NMR previously)
- 21 cm radio astrophysics
Note that the additional 5th day (beyond what you had in 8.13 during the Fall term) raises the level of expectations regarding the completion of "challenging" aspects of the lab guides and an expectation to exceed the standard material. There exist "extra" sessions at the end of the term in which students can acquire additional data or repeat selected portions of an experiment.
Required and Recommended Texts
- Experimental lab guides: available in the labs section.
- Bevington, Philip R., and D. Keith Robinson. Data Reduction and Error Analysis for the Physical Sciences. 3rd ed. Boston, MA: McGraw-Hill, 2002. ISBN: 9780072472271.
The Bevington and Robinson text contains a comprehensive treatment of error analysis and will be useful throughout your career.
Other Texts to Regularly Consult
- Melissinos, Adrian. Experiments in Modern Physics. 1st and 2nd ed. Burlington, MA: Academic Press, 1966 and 2003.
Material essential to the understanding of an experiment which can be found in the Melissinos text is generally omitted from the Lab Guide. Please consult both edition before and during your investigations (since each edition offers different material, you should consult them both!).
- Preston, Daryl, and Eric Dietz. The Art of Experimental Physics. New York, NY: John Wiley & Sons, 1991.
- Taylor, John. An Introduction to Error Analysis. 2nd ed. New York, NY: University Science Books, 1997.
This book covers much of the same material as Bevington and Robinson and is easier to read.
Reference Articles and Equipment Manuals
At this stage of your training as an experimentalist, you should realize that there is no "comprehensive" or perfect textbook. Much of the material you will need to dig into are the early journal papers which originally detailed many of these important discoveries. Many of these references are listed in the Labs Section. For more information on Technical Writing, please refer to The Mayfield Handbook for Technical and Scientific Writing.
Distribution of Junior Lab Experiments
- Scattering and quantization experiments
- Compton scattering
- Rutherford scattering
- Atomic physics
- Optical spectroscopy of hydrogenic atoms
- X-Ray physics
- Optical pumping (spring)
- The Zeeman effect (spring)
- Doppler-free spectroscopy (spring)
- Nuclear physics
- Quantum mechanics of alpha decay
- Neutron physics (spring)
- Mössbauer spectroscopy (spring)
- Condensed matter and statistical physics
- Pulsed nuclear magnetic resonance
- Johnson noise and shot noise
- Quantum information processing (spring)
- Superconductivity (spring)
- Special relativity and particle physics
- Speed and mean life of Cosmic-Ray Muons
- Relativistic dynamics
- 21 cm radio astrophysics (spring)
Expectations and Grading Policy
Attendance and Lab Performance - 10% Fall (8.13)/10% Spring (8.14)
The regularity of your attendance will be a factor in determining your grade in the course, as well as your preparedness for the measurements and alternating as the "lead" (with your partner), to carry them out.
It is essential that you efficiently use all of the laboratory time assigned to you, and sometimes more. An experienced experimental physicist will be present in every scheduled session. He or she will be assisted by a graduate teaching assistant. In addition, the Junior Lab staff includes technical instructors responsible for the maintenance of the equipment and the development of new experiments. We are ready and eager to help you make things work properly and answer questions.
Laboratory Notebooks - 10% Fall (8.13)/8% Spring (8.14)
One critical objective of this course is to instill habits of record keeping that will serve you well in future research. To this end you will use a standard experimental notebook in which the complete dated record of procedures, events, original data, calculations and results of every experiment is to be kept. No other form of notebook is acceptable in this course. Though you will generally work in pairs and are urged to collaborate in all aspects of carrying out the experiments and analyses, each student must keep a complete, dated record of each experiment and its analysis. The cross-hatched paper in the Computation Book is convenient for formatting tabulations, and for guiding line drawings and making rough plots. High resolution plots, photos, and copies of shared data should be glued or taped in place. You must write a sufficient narrative as the experiment proceeds so that, years later, you could reproduce the results you obtained. Notes, tables, and graphs should be neat and compact, leaving as little empty space in the lab notebook as is compatible with clarity and the logic of organization. There should be no loose sheets or graphs floating around.
Analyze data in the lab in a preliminary way as you go along to check for reasonableness. If you are making a series of measurements of one quantity as you vary another, plot the results as you go along so that you can see the trend, catch blunders, and judge where you may need more or less data. Repeat every measurement at least three times in as independent a manner as possible in order to establish a statistical basis for estimating random error and to reduce the chance of blunders. If you get through all the manipulations and preliminary analysis of an experiment in less than the four regularly assigned lab sessions, take the opportunity to perfect part or all of the experiment so as to obtain the best possible data set.
Many experiments will require you to transfer your data to a computer and store them in files on disk. Obviously, it is not practical in these cases to print out all your data and paste them into your notebook. However, we expect to see, in your lab notebook, representative plots or tables. In addition, we expect a clear description and summary of the data files so that when you return to the data days or weeks later, you are able to identify particular files with procedures you carried out in the lab.
Student notebooks will be evaluated three times during the Fall term (8.13). The first will follow the introductory experiments and be 'graded but not recorded' in order to help students learn what is expected. There will then be two recorded notebook evaluations, following the first and third main experiments. These will be conducted during lab sessions.
Each student's notebook will be evaluated twice during the Spring term (8.14): once following the first experiment and once following the third experiment. Students, having already taken 8.13, should be well versed in how to maintain their laboratory notebook.
Preparatory Questions and Data Analysis Assignments - 10% Fall (8.13)/10% Spring (8.14)
Each lab guide has a set of preparatory questions which point you to the essentials of the experiment. Before the first session of each experiment you are expected to work out the solutions to the preparatory problems and/or predictions in your lab book. Make a copy of your solutions and deposit it in your TA's mail box. It will be collected shortly after the start of the first session. Late solutions will not be accepted because you will need to know this material before the experiment. Your solutions will be graded by the graduate teaching assistant and returned at the next session. The Introductory Experiment preparatory questions will be graded for feedback but will not count towards your final course grade.
Oral Examinations (4 Private) - 30% Fall (8.13)/40% Spring (8.14)
During the Fall term (8.13), a one hour total length (2 students x 30 minutes each) oral review and discussion of each main experiment will be held between the pair of students and one or more of their instructors within 10 days of the last scheduled session for that experiment. To familiarize you with the procedure, a one hour oral will be held on one of the two introductory experiments of the students choice. This oral will proceed identically as the others and will be 'scored' but will not count towards the students final course grade. It is designed to give the student feedback on content, style, and presentation without the pressure of a graded performance. Partners should choose different introductory experiments for this initial oral exam. Videos of these practice orals will be used along with guidance and advice from lecturers from MIT's Program in Writing. Students should schedule a 1 hour appointment with one of these staff within the week following their practice oral for feedback.
Each student must bring to the exam session his or her lab notebook. Each student should prepare a 15 minute oral report on the theoretical and experimental aspects of a single portion of the experiment. Fifteen minutes is a short time, so it is essential that you rehearse your presentation as you would if you were giving a 15 minute paper at a meeting of the American Physical Society. Please review the Society guidelines. We suggest a maximum of ten slides and strongly suggest preparing your presentation electronically (e.g. LaTex or Microsoft Power Point) and using the LCD projector for the cleanest most professional presentation possible. The study materials section has detailed instructions and a template for generating your own presentations. The theoretical section should demonstrate a mastery of some portion of theory relevant to understanding the significance of the experimental results. The larger experimental section should dominate and demonstrate an understanding of how the equipment works, what was measured, how the data were reduced, and how the random and systematic errors were estimated. Each student must discuss motivating theory and experiment; it is not acceptable to discuss theory only or experiment only. Full cooperation with lab partners and others in preparing for the oral reports is encouraged. This latter aspect is particularly important to ensure that both partners report the same results!
During the Spring term (8.14), each student should prepare a 20 minute oral report on the theoretical and experimental aspects of a single portion of the experiment. This is a slightly longer presentation than in 8.13 and students are therefore expected to delve deeper into the physics and error analysis of their experiment.
Final Public Oral Presentation - 10% Fall (8.13)/Not Applicable Spring (8.14)
At the end of the term in December, each student will give a public oral presentation which will be attended by all students in the section. This public oral is a major component of the Communication Intensive in the Major (CI-M) requirement that 8.13 fulfills. This is in addition to the four jointly prepared oral presentations given to the section instructor. We have reserved the last week of class for this purpose. The public oral presentations should be given in the style of a paper presented at a conference, with careful attention paid to the preparation of material, usually in the form of an electronic presentation or transparencies, and to the clarity of the oral discussion. Questions from classmates and the audience are encouraged allowing for a general discussion of the experiment. Each student is required to make a 1 hour appointment at least four days prior to their public presentation where they should do a "dry run" and receive feedback. The dry run will not be graded, but failure to do it will result in a reduced grade for the oral presentation.
4-page Written Summaries - 30% Fall (8.13)/32% Spring (8.14)
You must email an Adobe® PDF copy of your, individually-prepared, written summary (=4 pages including figures) of the purpose, theory, and results of the experiment by midnight on the day you give your oral examination. The delay between oral exam and paper submission allows you to correct any egregious mistakes that were uncovered during the exam so as not to repeat them in your written work and receive a double penalty! All your work on the experiment should be summarized, not just the part you chose for your oral presentation. The individual summary you hand in should show evidence of your own mastery of the entire experiment, and possess a neat appearance with concise and correct English. Its organization and style should resemble that of a typical abstract that follows the title of an article in the Physical Review Letters. The abstract is essential. It should briefly mention the motivation (purpose), the method (how measured) and most important, the quantitative result with uncertainties. Based on those, a conclusion may be drawn. The report must be type-written in a form that would be suitable for submission as a manuscript and to aid you in this process we have produced a sample paper template written in LaTex that we encourage you to study and use for your own submissions.
The paper should include a discussion of motivation and the theoretical issues addressed by the experiment, a description of the apparatus and procedures used, a presentation of the results (including errors!), a discussion of these results, and, finally, a section briefly presenting your conclusions. This last section repeats what was stated in your abstract. The total length (including figures) of your summaries should not exceed four pages. It is easiest to read if you include figures and plots inline within the text and the sample paper template shows you how this is easily done. However, do not inundate the reader with material; you should find a way to summarize your results in at most two or three plots or tables. The figures and tables must be properly captioned. Material and ideas drawn from the work of others must be properly cited, and a list of references should be attached to the summary.
Papers will be graded using the following criteria:
- Theoretical and/or Experimental Motivation - 10%
- Description of Experiment - 40%
- Analysis of Data and Results - 40%
- Style and English - 10%
- Papers not submitted by midnight after the oral exam will be deducted 4% for each day they are late.
Ethics in Science and Science Education
When you read the report of a physics experiment in a reputable journal you can generally assume it represents an honest effort by the authors to describe exactly what they observed. You may doubt the interpretation or the theory they create to explain the results. But at least you trust that if you repeat the manipulations as described, you will get essentially the same experimental results.
Nature is the ultimate enforcer of truth in science. If subsequent work proves a published measurement is wrong by substantially more than the estimated error limits, a reputation shrinks. If fraud is discovered, a career may be ruined. So most professional scientists are very careful about the records they maintain and the results they publish.
Junior Lab is designed to provide preprofessional training in the art and science of experimental physics. What you record in your lab book and report in your written and oral presentations must be exactly what you have observed including date, time and who did it.
Sometimes you'll get things wrong because of an error in manipulation, equipment malfunction, misunderstanding, or a miscalculation. The instructor's job is to help you figure out what went wrong so you can do better next time. If circumstances in an experiment are such that you cannot get your own data (e.g. broken equipment, bad weather), you may use somebody else's provided you acknowledge it.
Fabrication or falsification of data, using the results of another person's work without acknowledgement, and copying from "the files" are intellectual crimes as serious as plagiarism, and possible causes for dismissal from the Institute.
The precaution about the acknowledgement of other people's data also applies to acknowledging other people's rhetoric. The appropriate way to incorporate an idea which you have learned from a textbook or other reference is to study the point until you understand it and then put the text aside and state the idea in your own words.
One often sees, in a scientific journal, phrases such as "Following Albert Einstein..." This means that the author is following the ideas or logic of Einstein not his exact words. If you quote material, it is not sufficient just to include it in the list of references at the end of your paper. You should use the following formatting:
The quote should be indented on both sides or enclosed in quotes, and attribution must be given immediately in the form of a reference note.
Importing text from a published work, from other student papers, or from the labguide without proper attribution is a serious breach of ethics and will be dealt with by the Committee on Discipline.
Most Junior Lab experiments are concerned with data comparison measurements of well known fundamental constants such as h, e, k, e/m, G, or significant physical quantities such as the mean life of the muon or the cross section of an electron for scattering a photon. The purpose of these experiments is to give you hands-on experience with atomic and nuclear phenomena, a sense of the reality of the concepts and theories you have studied in books and lectures, and the beginning of professional skill in obtaining and recognizing reliable data and extracting meaningful results from them. There is nothing wrong with "peeking" in the CRC Handbook or any of the many relevant texts to see what your experiment should have yielded. Indeed, the way to get maximum benefit from your Junior Lab experience is to play it as a game in which you squeeze the most accurate measurement you can get out of the available equipment and the practical limits of analysis, make a rigorous estimate of the error, and then compare the results with the established value. If the established value is outside your error range, try to find out what went wrong, fix it, and try again. If the established value is in your error range, don't rest easy, but do whatever may be necessary to prove it isn't an accident. Repetition is the essential key to attaining confidence and errors for a result, whether of a single measurement or an entire experiment! But whatever the outcome of an experiment is, you must tell exactly what you observed or measured when you present your oral or written report, regardless of how "bad" the results may appear to be.