Junior Laboratory PHYC 307L, Spring 2016 Webpage: - - PowerPoint PPT Presentation
Junior Laboratory PHYC 307L, Spring 2016 Webpage: http://physics.unm.edu/Courses/Becerra/Phys307LSp16/ Lectures : Mondays, 13:00-13:50 am, P&A room 184 Lab Sessions : Room 133 Monday 14:00-16:50 (Group 1) Tuesday 9:00-11:50 (Group 2)
Lectures: Mondays, 13:00-13:50 am, P&A room 184 Lab Sessions: Room 133 – Monday 14:00-16:50 (Group 1) – Tuesday 9:00-11:50 (Group 2) Instructor: Prof. Francisco Elohim Becerra email: fbecerra@unm.edu Office: P&A, room 1136 Teaching Assistant: Zhixiang Ren email: zxren@unm.edu Office: P&A, room 1132
Webpage: http://physics.unm.edu/Courses/Becerra/Phys307LSp16/
Office hours: arrange meeting with instructor or TA via email.
Lab course: experiments in modern physics for advanced undergraduates. Students will perform seminal experiments related to:
There are many good books. Some of the most useful ones:
– Basic elements of statistics – Probability distributions – Errors propagation and error analysis – Data analysis – Curve fitting – Hypothesis testing and Monte Carlo Simulations Homework Statistics; Data analysis and plotting; Error analysis; Line and Curve fitting; (Techniques in experimental physics)
6 experiments from 10 available. (Two-week period. Schedule in advance)
Before doing the experiment
For the experiment
Keep a clear, organized and complete lab notebook (see guidelines)
– Bound notebook – Use ink, and do not tear out pages. (Cross out sections not to be reviewed)
– Brief description of objectives and physics behind the experiment – Detailed description of experimental procedure and techniques, diagrams and plots. – Answer all questions of guide – Data collection, and data and error analysis. Include graphs – Detailed calculations, propagation of errors and estimated uncertainties – Results with uncertainties with units, and comparison with accepted values.
Formal reports are based on experiments that you performed. Should follow the style of a scientific journal (Typed, one or two columns)
– Abstract: concise description of methods and results. – Introduction: motivation, background and summary of experiment – Methods: description of experimental methods and calibrations – Data: present the data, use plots or/and tables – Results and data analysis: describe how the data analysis was done and present your results with errors – Discussion – Conclusion – References – Appendix if necessary
– Gain familiarity with formal writing style of scientific journals
12-minute Oral Presentation based on an experiment. It will be followed by questions from students, TA and instructor.
– Motivation – Theoretical background – Brief description of the experiment – Brief description of data collection process – Results and discussion with error analysis – Application of the physics learned in technology /fundamental research – Conclusion
– Strengthen your communication skills – Think how to present your results to a broad audience and defend your ideas
Lab Notebook 40% 3 Formal Reports 40% Homework 10% Oral Presentation 10% Total 100%
Tentative schedule (subject to revision) Please check course website for updates Lab notebooks revision/Formal reports 1st 02/29 (M)/03/01 (T) Lab notebook (Exp. 1 & 2) 03/03 (Th) Draft 1st Formal Report (email 5pm) 03/11 (F) 1st Formal Report (email 5pm) 2nd 04/04 (M)/04/05 (T) Lab notebook (Exp.) 3 and 4 04/07 (Th) 2nd Formal Report (email 5pm) 3rd 05/02 (M)Lab notebook (Exp.) 5 and 6 05/04 (W) 3rd Formal Report (email 5pm) Oral presentations at the end of the semester
Late work policy: Late work within 3 days after the deadline is accepted for 50% of the grade. No grade is given after that.
shoes, etc.)
cause irreversible damage to equipment and can cause an accident when working with or near HV equipment.
equipment to the lab instructor or the TA.
and or radioactive materials).
cables or equipment.
safety concerns of each experiment and any special instructions for working with sensitive equipment.
Webpage: http://physics.unm.edu/Courses/Becerra/Phys307LSp16/
Goal of an experiment 1.- Perform a measurement of a parameter. All measurements are subject to uncertainties.
(correctness of a result)
any reference to the true value 2.- Hypothesis testing: Confidence level; Goodness of the fit? Example: speed of light
Best value (mean) Uncertainty Units Use no more that 2 significant digits in the error Precision
% 5 09 . 3 15 . s m c / 10 ) 15 . 09 . 3 (
8 exp
2 4 6 8 10 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4
Uncertainty Mean (Cexp) True value (C) c Accuracy Probability Distribution
Measurements cannot be performed with Zero Error. (a) Statistical errors. Random fluctuations: (in either direction) Due to Intrinsic noise of random processes, precision device limitations, etc… (b) Systematic errors. Inaccuracies: (consistently in one direction) Reproducible inaccuracies resulting in a bias of our measurement result. Due to the instruments or experimental conditions (calibrations) Report measurement result with estimated uncertainty Any measurement has limitations. Uncertainties specify these limitations.
2 2 2
systematic l statistica c
Report separately or add in quadrature:
Measurements cannot be performed with Zero Error. (a) Statistical errors. Random fluctuations: (in either direction) Due to Intrinsic noise of random processes, precision device limitations, etc… (b) Systematic errors. Inaccuracies: (consistently in one direction) Reproducible inaccuracies resulting in a bias of our measurement result. Due to the instruments or experimental conditions (calibrations) Report measurement result with estimated uncertainty Any measurement has limitations. Uncertainties specify these limitations.
2 2 2
systematic l statistica c
Report separately or add in quadrature:
Measurements cannot be performed with Zero Error. (a) Statistical errors. Random fluctuations: (in either direction) Due to Intrinsic noise of random processes, precision device limitations, etc… (b) Systematic errors. Inaccuracies: (consistently in one direction) Reproducible inaccuracies resulting in a bias of our measurement result. Due to the instruments or experimental conditions (calibrations)
Statistical errors Repeated measurements are distributed according to a Normal (Gaussian) about the mean.
2 4 6 8 10 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4
Mean c Accuracy q1 q2 Gaussian Prob. Distribution q3
q i q
q
2 ) (
2
Always report measurement result with estimated uncertainty!
q
(small systematic errors)
Assume N measurements of the physical quantity . The best estimate of is the Mean:
Variance: estimate of uncertainty:
Example: Time an atom decays and emits a photon:
} ,... , {
2 1 N
q q q
N i i
1
N i i q
1 2 2
True
q
True
q q
ns t 12 . 24
(a) 59 . 3 ) ( 15 1
16 1 2
i i t
t t (b)
ns t ) 6 . 3 1 . 24 (
exp
Data (N=16): t={20,17,24,23,25,31,25,24,23,26,19,23,26,29,28,23} ns.
t
t t
exp
(multi-variable function “q”) Suppose where are independent (uncorrelated) quantities
) ... , , , (
3 2 1 N
x x x x q q
Example: Determine R when measuring I and V:
} {
i
x
i
2 1 2 2 i N i i q
x q
(xi uncorrelated variables)
I V R
A I ) 45 . 29 . 1 (
exp
V V ) 5 . 3 . 3 (
exp
55 . 2 I V R
2 , 2 , 2 2
946 .
I V I I V V R
I R V R
q
q
i
q
IR V 79 . 15 .
97 .
R
Measurement Transient response of RC circuits to step voltages
Study response of RC circuits to sinusoidal signals; cutoff frequency
Study response of RC circuit below
Lab notebook: proof that the experiment was carried out in the manner described in the scientific paper or in the lab report. All the details of the experiment, results and analysis must be in the lab
your lab notebook. All experiments require detailed calculations, derivations and complete error analysis, regardless of whether you are doing the formal report for a particular experiment.
If Systematic errors are small: Errors distributed as Gaussian with variance σq 2.
q
True
q q
q True True q
q ,
q True True q
q 2 ,
q True True q
q 3 ,
is 68% is 95.5% is 99.7% If differs from by >3 σq: probability of happening ~0.3% (very unlikely) (1) Unknown systematic (2) Theory is not complete or wrong
True
q
True
q
wiki Confidence Level
Exp
q