Modern Physics Lab
Modern Physics Lab
Instructor Modern Physics Lab
• Brian Zulkoskey Rm 115 Physics 966-6439
[email protected]
Fall 2010 Introduction
Modern Physics Lab
Lab Location
Modern Physics Lab
Lab Sectioning
• The Modern Physics lab is held in Rm 45 Physics, downstairs in the west hallway of the new part of the building. • The room has a main area and numerous cubicles housing individual experiments.
• There are Thursday and Friday lab sections for Phys 251 • Wednesday and Friday lab sections for Phys 381. • Lab start time is somewhat flexible. Anyone who can start at 1:30 pm should, but starting the lab at 2:30 pm is also acceptable (but must start at either 1:30 pm or 2:30 pm!)
Modern Physics Lab
Lab Groups/Partners • Work in groups of two (preferable) or three. • Be sure your partner can start the lab at the same time as you. • Indicate the time you plan to start the lab on the sign-up sheet.
Modern Physics Lab
Lab Schedule • LAB SCHEDULES WILL BE POSTED EARLY NEXT WEEK • Each group does a different lab each week. Although most of the lab material will eventually be covered in class, it is likely that you will encounter it in the lab first (especially for the first few labs). The lab manual has been written with this in mind.
1
Modern Physics Lab
Modern Physics Lab
Safety Issues Lab Materials • Modern Physics lab manuals are available on the web at http://physics.usask.ca/~bzulkosk/modphyslab/ • At least 2 graph notebooks (3 books if you want to do a written pre-lab for your 3rd experiment) • scientific calculator • geometry set (protractor, compass, straight edge)
• • • • •
High voltage Radioactive sources X-ray sources Lead bricks When you come to the lab, examine the equipment, decide on your procedure, then consult with the instructor before starting the experiment or adjusting the equipment. The equipment is more sophisticated than what you have used in previous labs, and this also means it is more sensitive and delicate (and expensive and potentially dangerous).
Modern Physics Lab
Modern Physics Lab
Report Format
Report Format • • Heading – your name, partner(s) name, date, title of experiment
• Rough Data – first page of report – value, units, error
• Object – purpose and how it will be accomplished
Theory – short paragraph describing the theoretical concepts involved in the data analysis and interpretation. – state equations used in analysis and define variables in equations – e.g. Millikan: Analysis of the forces acting on a charged oil drop allows the calculation of its charge. Then state equations for drop charge and define variables.
Modern Physics Lab
Modern Physics Lab
Report Format •
Report Format
Experiment – – – –
diagram and brief explanation of equipment 2 or 3 sentences summarizing the procedure good copy of data e.g. Millikan: Rise and fall times in the presence and absence of an electric field are measured for 10 oil drops moving a known distance.
• Analysis – sample calculations are still required if a computer program is used. – tabulate values whenever possible.
2
Modern Physics Lab
Modern Physics Lab
Report Format Report Format
• Discussion – HOW WELL DO YOUR RESULTS COMPARE WITH ACCEPTED OR THEORETICAL VALUES? – SOURCES OF ERROR – State numerical results with exp. error – Compare with accepted or theoretical values where possible. (CRC Handbook of Chemistry and Physics) – Discuss any factors not included in error calc'ns which may affect results. – If values don't agree, attempt an explanation.
• Discussion (cont.) – e.g. Millikan: The values obtained for the oil drop charges were found to be integral multiples, within error, of a unit charge of ________ _________ C. This agrees within error with the elementary charge of 1.602 10–19 C.
Modern Physics Lab
Modern Physics Lab
Report Format •
Report Format
Conclusion – WHAT DO YOUR RESULTS MEAN? – Discuss results (observations as well as numbers) in terms of the predictions of theory. – In some cases the numerical results may disagree with theoretical or accepted values, but the trend of the data (linear, exponential) may agree. – Rather than being too specific, decide if your results verify some basic physical concept.
•
Conclusion (cont.) – HOW WELL DID YOU PERFORM THE EXPT? (any problems?) – CONSTRUCTIVE CRITICISM AND SUGGESTIONS. – APPLICATIONS OF THIS TYPE OF EXPT OR RESULTS. – e.g. Millikan: The observation that oil drop charges only occurred in integral multiples of an elementary charge verifies the quantization of electric charge.
Modern Physics Lab
Modern Physics Lab
Report Format General Notes
• Summary (Abstract) – – – – – –
Answers the questions: WHAT DID YOU DO? HOW DID YOU DO IT? WHAT WERE YOUR RESULTS? WHAT IS THEIR SIGNIFICANCE? e.g. Equipment consisting of _________ was used to measure __________. Values of ___________ were obtained. Comparing these values with the values calculated from theory (_______) led to the conclusion that _________ had been verified.
• •
•
DON'T COPY FROM THE MANUAL READ THE MANUAL BEFORE COMING TO THE LAB. Experiments require preparation before the lab period. DON'T LEAVE WRITING YOUR REPORT UNTIL THE DAY BEFORE IT'S DUE! Allow yourself a few days so that you can see me if you need help.
3
Modern Physics Lab
Modern Physics Lab
General Notes
General Notes •
LAB REPORT POLICIES: – reports are due at beginning of next lab period – DO NOT COME LATE TO THE LAB, OR WORK ON ANOTHER EXPT IN THE LAB. – COPYING OR USE OF OLD LAB NOTEBOOKS WILL NOT BE TOLERATED (mark of 0). – labs up to one week late: –5 – labs more than one week late: credit, but not graded (0)
• • •
•
Complete lab exemptions: minimum 70% YOUR COMMENTS ARE WELCOME. The experiments are continually being revised. If you have suggestions on ways the lab can be improved, please talk to me. READ THE GENERAL INTRODUCTION IN THE MANUAL BEFORE FIRST LAB: – Discusses error calculations, graphs, conversion of units, tables, and format. – Use calculus method of error calculation (addition in quadrature)
4