Transcription of EXPERIMENTAL PHYSICS Notes for Course PHYS2350
1 EXPERIMENTAL PHYSICSN otes for Course PHYS2350 Jim NapolitanoDepartment of PhysicsRensselaer Polytechnic InstituteSpring 1999iPrefaceThese Notes are meant to accompany Course PHYS2350 EXPERIMENTAL PHYSICS ,for the Spring 1999 semester. They should make it much easier for you to fol-low the material and to be better prepared for the experiments. The coursewill notcover everything in these Notes , but with some luck the Notes willcontinue to be a useful reference for text is organized into two types of major sections, namelyChaptersandExperiments, so that they follow in a more or less logical order. As muchas possible, the Experiments only rely on material in preceding is no index, but hopefully the table of contents will be good enoughfor the time to helpful comments from many students and faculty, this hasall gone through a number of revisions which I hope have made the materialmore useful and more clearly presented.
2 In the latest version, I've reformattedeverything into LATEX2e, the new LATEX standard. For the time being, I'veremoved the explicit distinction between \Experiments" and \Chapters", butthe references should still be clear. (My apologies for any mistakes I've madewhich I didn't nd in time!) This change allows me to use what I think aremore a more clear postscript thanks to Prof. Peter Persans for his comments, and for addingthe Jarrell{Ash spectrometer to the laboratory for theAtomic Spectroscopymeasurement. I've updated the \Procedure" section of that experiment toinclude a description of this instrument. Credit also goes to Peter for theexpanded appendix giving a quick review give me any comments you might have on these Notes , particularlyif you see ways in which they may be for your Napolitano, January 3, 1999iiValues of Physical ConstantsThe following table of fundamental constants is taken from the \Review ofParticle Properties", published in Physical Review D I, (1994).}
3 Theuncertainties in the values are very small and can be neglected for the exper-iments in this of light in vacuumc299792458 m/secPlanck's 10 34 Jsec h=2 10 22 MeV secElectron 10 19 Coul 10 13 MeV mVacuum permittivity 08:854187817 10 12F/mVacuum permeability 04 10 7N/A2 Electron MeV/c2 Proton MeV/c2 Deuteron MeV/c2 Atomic mass MeV/c2 Rydberg eVBohr magneton 10 11 MeV/T=e h=2meNuclear magneton 10 14 MeV/T=e h=2mpAvogardro 1023atoms/moleBoltzmann 10 23J/KContents1 Data Taking and YourLogBook .. CommonSense .. Use Redundancy .. Be Precise, But Don't Go Overboard .. MeasureRatios .. AvoidPersonalBias .. TablesandPlots .. Tables of Data and Results .. MakingPlots.
4 UsingComputers .. ProgramsforthePC .. FormalLabReports .. 192 Basic Electronic Voltage,Resistance,andCurrent .. TheVoltageDivider .. CapacitorsandACCircuits .. TheGeneralizedVoltageDivider .. Inductors .. DiodesandTransistors .. 383 Common Laboratory BasicConsiderations .. DC Power Supplies .. Oscilloscopes .. SweepandTrigger .. Input Voltage Control .. DualTraceOperation .. Digitizers .. ADC' DeadTime .. Digital Oscilloscopes .. The LeCroy 9310 Digital Oscilloscope .. ComputerInterfaces .. 644 Experiment 1: The Voltage 725 Experiment 2: The Ramsauer Transmission past a One Dimensional Well.
5 ThreeDimensionalScattering .. Procedure .. AdvancedTopics .. 856 EXPERIMENTAL SystematicandRandomUncertainties .. Propagation of Errors .. DominantUncertainty .. Experiment 3: Gravitational Gravity and the Pendulum .. PrincipleofEquivalence .. MeasurementsandAnalysis ..1108 Experiment 4: Dielectric Constants of ElectrostaticsofGases .. Procedure .. AdvancedTopics ..1269 Statistical CurveFitting .. StraightLineFitting .. FittingtoLinearFunctions .. 2astheGoodnessofFit .. CovarianceandCorrelations .. Distributions .. The Binomial Distribution .. Data Analysis Experiment 5: Resistivity of 'sLaw .. ResistanceandResistivity.
6 TheEddyCurrentTechnique .. Procedure ..17511 Light Production and Thermal Radiation .. Lasers .. PhotographicFilm .. PhotomultiplierTubes .. Experiment 6: Atomic Energy Levels of the Hydrogen Atom .. Corrections .. Procedure: Baird Spectrograph .. Procedure: Jarrell{Ash Spectrometer ..22213 Noise and Noise .. Example: Background Subtraction .. 1=fNoise .. Frequency lters .. Negative Feedback and Operational Ampli ers .. TheLock-InAmpli er .. Experiment 7: Johnson Thermal Motion of Electrons .. Procedure .. FrequencySpectrum .. CircuitModi Experiment 8: The Faraday Magnetically Induced Optical Rotation .. Electromagnetic Waves and Polarization .. Light Propagation in a Medium.}
7 TheFaradayE Polarization Calibration ..28516 Experiment 9: Nuclear Magnetic Nuclear Magnetism and Precession .. Equipment Settings and Parameters .. Procedure and Analysis .. Elementary Particle .. PhotonsandElectrons .. RadiationSafety .. SolidAngle .. Gaseous Ionization Detectors .. Scintillation Detectors .. Ampli Discriminators and Single Channel Analyzers .. ProcessingLogicSignals .. Experiment 10: ParticleCountingStatistics .. Detecting Radiation .. HalfLifeMeasurements ..34819 Experiment 11: Positron Correlated Pairs of ProcedureandAnalysis .. Angular Correlation in60Co ..37020 Experiment 12: The Compton .. Relativistic Kinematics .. Classical and Quantum Mechanical Scattering.
8 Procedure .. Recoil Electron Detection .. Extracting the Di erential Cross Section .. 393A Principles of Quantum Photons .. WavelengthofaParticle .. Principles of Statistical TheMaxwellDistribution ..406C Principles of Natural Logarithms .. ComplexVariables ..416D A Short Guide to AMATLABR eview .. MakingFancyPlotsinMATLAB .. Drea'sHandleGraphicsPrimer ..425Ch 1 Data Taking and PresentationProgress is made in the physical sciences through a simple process. A modelis developed, and the consequences of the model are calculated. These con-sequences are then compared to EXPERIMENTAL data. If the consequences donot agree with the data, then the model is wrong, and it should be enough successful comparisons with data, however, a model becomeswidely accepted, and progress goes on from , it is crucial that the data be \correct".
9 Furthermore, the accu-racy of the measurement must also be reported so that we know how stronga comparison we can make with the model. Finally, since it is likely thatmany people will want to compare their models to the data, the experimentalresults must be reported clearly and concisely so that others can read andunderstand purpose of this chapter is to give you some ideas on how to takedata \correctly", and how to report it clearly. However, every experiment isdi erent, so these guidelines can only serve as a broad basis. You will gainexperience as you do more experiments, learning rules for yourself as you will use some loose language, especially in this chapter. ExperimentalPhysics is a subject that can only be truly learned from experience, and termslike \settings" and \uncertainties" will become much clearer when you've12CH 1.
10 DATA TAKING AND PRESENTATION done your time the laboratory. However, we attempt to at least roughlyde ne terms as we go along. For starters, we take the term \quantity" to bethe result of some measurement, like the number read o a meter stick or avoltmeter. Things that you can change by hand, which a ect the \quantity"you want to measure, are called \settings".I will often resort to saying something like \.. and your intuition will getbetter after some experience." I apologize, but it is very hard totellsomeonehow to be a good experimenter. You have to learn it by being shown how,and then working on your own. There is at least one book, however, whichcontains many good ideas about carrying out experiments: Practical PHYSICS , G.
