Physics Laboratory & Research

As Taught in:

2020/2021

Level:

undergraduate

Learning Source Types:

=> Lab Notes

=> Readings Resources

=> Practice

Course Overview:

Physics laboratory consist of two courses in experimental physics. The course sequence is usually taken by undergraduates. Officially, the courses are called Applied Physics, and due to some extend it become a Physics Laboratory and Research.

Each semester, learners do experiments on phenomena whose discoveries led to major advances in Physics. In the process, learner deepen their understanding of the relations between experiment and theory, mostly in the practical physics.

Prerequisites:

Physics PTL – Physics Theories and Laboratory

Physics 106 – Advanced Quantum Mechanics

Course Goals:

The purposes of Physics Laboratory & Research are to give learners hands-on experience with some of the experimental bases of modern physics, deepening learner understanding of the relation between experiment and theory, and — in the process — to accelerate learner professional development as a scientist in skills such as oral and written communication methods, the troubleshooting process, professional scientific attitude, data analysis, and reasoning about uncertainty.

Learner will do experiments on phenomena whose discoveries led to major advances in physics. The data learner obtain will have inevitable systematic and random errors that obscure the relations between the macroscopic observables of our sensory experience and the physical laws that govern the submicroscopic world of atoms and nuclei. Learner will be challenged to learn how each of the experimental setups works, to master its manipulation so as to obtain the best possible data, and then to interpret the data in light of theory with a quantitative assessment of the uncertainties. We believe learner will find satisfaction in observing, measuring, and understanding phenomena many of which would have won you the awards if you had discovered them.

Team Work:

Learner 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 learners find they require at least 18 hours a week to do the work of the course.

Laboratory Access:

Appointment will be required to discuss Physics and maintain equipment, especially the security of radioactive sources.

It is each learner’s responsibility to maintain security by making sure the lab are keep locked at all times outside of the regularly scheduled sessions.

One should never work alone in a laboratory, especially if high voltages are involved. A partner or instructor must be within reach.

Ethics in Science and Education:

Nature is the ultimate enforcer of truth in science. You will be tempted many times in Physics Lab to tamper with the integrity of your scientific results. Do not. This hurts yourself and others. Learner may also be tempted to plagiarize materials for your oral and written reports. Do not. All instances of academic misconduct in Junior Lab will be punished severely. Learners are highly encouraged to review the materials on the website or educational institute academic integrity website.

Please consult your instructor, supervisor, or class assistant more about the ethics in science and education section, which learner are obligated to understand, especially for more specific to discussion.

Safety in Lab:

Learner safety in Physics Lab is the Educator’s top priority. It should be your top priority, too. The most important safety rules, which the educator will enforce diligently, are as follows:

1. Never work alone.
2. No eating or drinking in the lab.
3. Treat radioactive sources according to the ALARA principle, as per your training.
4. Obey state regulations and Physics Lab practices on access and tracking of radioactive sources, as per your training.

On the first week of PLR, Physics Lab learners receive a general safety discussion, a lab tour, and a formal state-mandated training in the use of sealed sources of ionizing radiation from a member of  Physics Lab Radiation Protection Program. This training is required for work in PLR & PTL (Physics Theory and Laboratory). Learners who will be performing experiments using biological materials, lasers, or requiring access to the Nuclear Reactor facility will require further formal training from Official Office of Environment, Health and Safety at the location. The Physics Lab staff will provide information on the required training as needed.

In particular, the ‘Doppler-Free Saturated Absorption Spectroscopy’ experiment utilizes a near-IR laser operating at 40 mW of output power; the ‘Raman Spectroscopy’ experiment utilizes a  532 nm 2 W laser. As such, all users of these experiments must undergo Physics Laser Safety Training, about 1.5 hours in length, offered by EHS (Environmental Health and Safety) every few weeks prior to performing the experiment. All learners should download the Laser Safety manual and read.

Please consult the more extensive safety in the Physics Lab — which you are obligated to understand — for more specific discussion.

Regular Experiments in this Course would be like:

• Optical Pumping of Rubidium Vapor
• Pulsed NMR: Spin Echoes
• Mōssbaure Spectroscopy
• X-Ray Physics
• Superconductivity
• 21-cm Radio Astrophysics
• Doppler-Free Laser Spectroscopy
• Quantum Information Processing
• Optical Trapping
• Raman Spectroscopy

Unlike other Courses, in this course, readings get split as shown:

Required Readings

Bevington, Philip R., and D. Keith Robinson. Data Reduction and Error Analysis for the Physical Sciences. Boston: McGraw-Hill, 2003. ISBN: 9780072472271.

Experimental Lab Manuals by the Physics Lab staff (available inside every Experiment page)

Ethnics in Science and Education by the Science Lab Staff

Laboratory Safety and Regulations in Physics Lab by the Physics Lab Staff

Recommended Readings

Melissinos, Adrian Constantin. Experiments in Modern Physics. New York: Academic Press, 1966. (Out of print. May be available in academic libraries.)

Melissinos, Adrian Constantin, and Jim Napolitano. Experiments in Modern Physics. San Diego: Academic Press, 2003. ISBN: 9780124898516.

*Please do consultation before and during your investigations. Those text is only recommended because our experience feels it is a bit too challenge to “require”. 

Other Useful Readings

Preston, Daryl, and Eric Dietz. The Art of Experimental Physics. New York, NY: John Wiley & Sons, 1991. ISBN: 9780471847489.

Taylor, John Robert. An Introduction to Error Analysis: The Study of Uncertainties in Physical Measurements. Sausalito, CA: University Science Books, 1997. ISBN: 9780935702750. (This book covers much of the same material as Bevington and Robinson and is easier to read.)

Gregory, Philip Christopher. Bayesian Logical Data Analysis for the Physical Sciences: A Comparative Approach with Mathematica^® Support. Cambridge, UK: Cambridge University Press, 2006. ISBN: 9780521841504.

Maintaining an experiment notes is one of the most important skills you will acquire in Physics Lab. A good notes is essential when Learner begin to develop papers or oral presentations summarizing learner experimental efforts. A detailed, real-time narrative that includes experimental schematics, plots of raw data, and details of your analysis will enable leaner to receive quick feedback and assistance from partner, staff, and educators.

Non-manageable or non-organize notes will prove immensely challenging to learner and educator. It is very complex to answer questions like, “What bring the errors to the experiment”, or “Why was the experiment and the theory did not match at some order of magnitude?” without being able to clarify and friendly trace learner efforts using the notes. Don’t count on being able to recall any items and equipments setting even one day after a lab session! The following is a list of guidelines to follow when performing laboratory work.

1. Create a descriptive table of contents and make an entry every time you add new material. Title the TOC with the following:

   Date………………………Contents………………………Page

   Don’t use generic entries like “Day 1” or “Analysis.” Instead, produce records of significant milestones: e.g., “Plot of monochromator linearity over the visible spectrum,” or “Monte Carlo simulation of muon mean slant path distance.” Such descriptive headings will prove enormously useful later on when reviewing your notebook.

2. Sign every page and date every entry to demonstrate authenticity.

3. Don’t ever erase, use pencil, use white-out, or tear out pages of a lab notes. Indicate “mistakes” by simply drawing a single, neat line through the item: they may prove to be not so incorrect as initially thought. Documented errors are useful as a guide to how the experiment was done and provide clues on how to better execute the experiment next time.

4. Loose-leaf pages are never acceptable within a lab notes. Printouts generated by computer must be neatly taped into the notes.

5. Handwriting should be legible to at least learner-self, and ideally to others. The notebook need not be a linear narrative, but it should be neat, compact, and orderly.

6. If not completed online, preparatory questions and solutions should be written in learner lab notes.

   Setup: (things to do when starting each experiment)

7. Following the preparatory work, state the essential physics of the experiment in your own words. List your experimental objectives and how they relate to the essential physics.

8. After listing the objectives, identify the procedures you will have to perform, the data you must obtain, and the required calibrations.

9. When starting a new experiment, sketch a block diagram of the apparatus and signal chain.

   Experimental documentation: (recording your work)

10. Record extensive narrative of your experimental work, in and out of lab. Describe what you did, why you did it, what you saw, and what you did next. Note typical instrument settings so as to be able to quickly set up an experiment on subsequent days. Sketch waveforms at various places within the signal chain. This will help ensure your understanding of each component and permit you to rapidly identify equipment failure.

11. Tabulate data into columns with headings, units, and estimated measurement uncertainties. Tables of raw data are the core of your notebook, but it must be more than just a data log.

12. Identify the location of large data files or long analysis programs if they are too big to directly enter or tape into your notes. Analysis scripts, functional forms for non-linear fits, etc., should always be present in your notes.

13. Don’t wait until after the lab session has ended to visually examine the quality of your data. Create hand drawn plots of data — with error bars— as they are acquired, not later. These initial plots will inevitably save you time and frustration in making sure that your data are reasonable and suggestive of the behavior you expect. The importance of making preliminary plots and analyses in real time cannot be overstated.

14. Your notebook should contain your analysis, results, and conclusions. These should be documented with narrative, formulas, computations, plots, and error estimates, just like in-lab work. Remember to annotate graphics with as much information as possible about how they were created.

Bring your notes to every lab session and to all oral exams. Failure to do so may result in penalties to your results!

Introduction

Your safety in Physics Lab is the everyone top priority. It should be Learner-self top priority, too. We are fortunate that there has never been a serious injury in Physics Lab. Prevention of injury is a matter of being aware of and having respect for pieces of equipment that are potentially dangerous. Nevertheless, setting up a reasonably comprehensive and interesting set of experiments in modern physics without using potentially hazardous equipment is virtually impossible. Therefore, being aware of the hazards and exercising appropriate cautions is essential for all learners, educators, and staffs.

Beyond the specific safety procedures listed below, learner must also obey the following general rules in Physics Lab:

• No eating, drinking, or other hand-to-mouth action in the lab. Leave all food items outside the lab or in a closed container like a backpack.
• No working without properly trained lab staff present. Do not work alone. No unauthorized access, after hours or otherwise.
• No bare feet. No pets.
• Treat radioactive sources according to the ALARA principle, as per your training.
• Obey state regulations and Physics Lab practices on access and tracking of radioactive sources, as per your training.

On the first day of PTL, Physics Lab learner receive a general safety discussion, a lab tour, and a formal state-mandated training in the use of sealed sources of ionizing radiation from a member of Education Radiation Training Program. This training is required for work in both PTL and PLR. Learners who will be performing experiments using biological materials, or lasers, or requiring access to the other facility will require further formal training from Official Office of Environment Health and Safety. The Physics Lab staff will provide information on the required training as needed.

Chemical Hygiene and Environmental Safety

You will not prepare chemical samples or generate hazardous chemical waste in Physics Lab. You may occasionally use closed samples prepared by the lab staff which — in the highly unlikely event of a spill — could constitute hazardous waste. Do not attempt to clean up or dispose of chemical spills in Physics Lab. Ask for help from the lab staff, all of whom have the required training for dealing with this situation. Improper disposal of hazardous material in the trash or lab sink could result in environmental contamination and unnecessary exposure of other people to chemical hazards.

The lab staff are responsible for maintenance and awareness of all hazardous substances in the lab. Do not bring any potentially hazardous substances into lab without first consulting the staff. Hazardous substances are those which are flammable, reactive, toxic, radioactive, or environmental pollutants. Do not generate unlabeled containers of any substance — hazardous or not — in any lab space. Unlabeled containers must be treated as containing unknown substances. This triggers worst-case assumptions and expensive disposal protocols.

Electrical Safety

The first rule of electrical safety is to never work alone. All high voltage supplies are clearly marked as dangerous. Do not poke or probe into them. Turn off the supply if you need to change cable connections. The supply may be dangerous even when turned off if the capacitors have not discharged; always keep one hand in your pocket when testing any circuit in which there may be high voltages present so that if you get a shock, it will not be across your chest. Never go barefoot in the lab. Remember that it is current that kills. A good (e.g. sweaty) connection of 6 volts across your body can kill as well as a poor connection of 600 or 6000 volts if the power supply can generate sufficient current.

The ampere is a large unit of current. The details of an injury will depend not only on the current value, however, but also on its frequency and the path of the current through the body. Currents below 1 mA are generally safe, while painful injuries will generally result from currents as low as 10 mA. Common lore holds that 100 mA is the lower threshold for “deadly current”, but ventricular fibrillation can begin as low as 30 mA. Circuit breakers on electrical wall sockets are typically 15 A or 20 A, and will therefore not protect a person from injury.

Cryogenic Safety

Liquid nitrogen, boiling at 77 K, is chemically inert, but it can cause severe frostbite. Wear gloves and protective glasses when transferring or transporting liquid nitrogen. Splashing against the skin should be avoided as much as possible, but it is generally not dangerous because the liquid will boil away rapidly, leaving only cold gas which will not transfer heat to the skin efficiently enough to cause injury. However, pooling of the liquid against the skin for even a short time will cause injury, and care must be taken to avoid this situation. Ultimately, the most ready source of injury when working with liquid nitrogen or other cryogens is not the liquid itself, but rather touching the cold metal surfaces of uninsulated valves and transfer vessels.

Liquid helium, boiling at 4.2 K, requires significantly more careful handling than liquid nitrogen, and should not be manipulated by Physics Lab learners. When the cap on a liquid helium Dewar is left off, air flows in and freezes in the neck, forming a strong cement. When a probe is inserted, it may be frozen in solid. Pressure will then build up until something explodes. During the PLR ‘Superconductivity’ experiment, never leave the Dewar cap off for more than a few seconds. Always ream out the Dewar before you use it. Check periodically to see that the probe is free. If the probe should freeze in the Dewar, get help immediately from any of the Physics Lab staff or educators.

Laser Safety

A laser beam may not seem very bright, but if it enters your eye it will be focused by the lens of your eye to a pinpoint spot on the retina where the intensity is sufficient to destroy retinal cells. It is wise to terminate a laser beam with a diffuse absorber so that the beam does not shine around the room. Never examine the performance of an optical system with a laser by viewing the beam directly with your eye or reflector.

Learners who perform the ‘Doppler-Free Saturated Absorption Spectroscopy’ or ‘Raman Spectroscopy’ experiments in PLR require additional laser safety training from EHS, which must be completed prior to performing the experiment: EHS Course Laser Safety, about 1.5 hours in length, offered by EHS. The ‘Doppler-Free’ experiment utilizes a near-IR laser operating at 40 mW of output power. As such, it is classified as a Class 3b laser. The ‘Raman Spectroscopy’ experiment utilizes a 532 nm (green) laser operating at 2 W, placing it in the highest laser safety category, Class 4. Class 3b and Class 4 lasers require special safety training to operate. All learners should readings the Physics Lab Laser Safety Manual, at a minimum, Section Two.XVI.D dealing with Class 3b laser controls.

Biological Safety

Physics Lab is classified as a BL1 (Biohazard Safety Level 1) laboratory space, meaning that specific areas of the laboratory are authorized under the Biosafety Program for use of specific minimally infectious pathogens. (No human tissues are allowed.) Learners who perform the ‘Optical Trapping’ biophysics experiment are required to complete EHS Course General Biosafety for Researchers or Undergraduate Teaching Lab Biosafety before beginning work on the experiment. A Lab Biosafety training session with a member of the Biosafety Program will be organized early in the semester by the Expert in Physics Lab staff for all learners who require it.