fysikexperiment i forskning och samhälle, ht 2013
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Fysikexperiment i forskning och samhälle, HT 2013. What defines physics? What defines a physics experiment?. Consider and discuss in groups the two questions above. Define a couple of points as answers to the questions. The teachers’ answers. What characterises physics? - PowerPoint PPT PresentationTRANSCRIPT
Fysikexperiment i forskning och samhälle, HT 2013
Lunds universitet / Fysiska institutionen / Fysikexperiment i forskning och samhälle FYSN11, HT 2009
What defines physics? What defines a physics experiment?
Consider and discuss in groups the two questions above. Define
a couple of points as answers to the questions.
Lunds universitet / Fysiska institutionen / Fysikexperiment i forskning och samhälle FYSN11, HT 2009
The teachers’ answers
What characterises physics?
• Striving for understanding and formulating the principal laws of nature• Understanding the physical entities relevant for a physical system• Understanding the nature of and interactions between these entities
Lunds universitet / Fysiska institutionen / Fysikexperiment i forskning och samhälle FYSN11, HT 2009
What characterises a physics experiment?
•Control over cause – action•Controlled conditions: Control of as many parameters as
possible – systematic change of parameters • Idealisation / Abstraction •Reproducibility•Fundament in theory and/or model•Deliberate perturbation of a system in order to determine
the system’s characteristics. Make the cause-study the action
The teachers’ answers
Lunds universitet / Fysiska institutionen / Fysikexperiment i forskning och samhälle FYSN11, HT 2009
Boxes
Think of physics experiments that could deliver information about the box and its contents.
Which physical property would you like to determine?How would you determine this physical property?Why does your measurement allow measuring this particular physical property?What is the length scale of the physical property?What is the length scale of your experiment?
Lunds universitet / Fysiska institutionen / Fysikexperiment i forskning och samhälle FYSN11, HT 2009
Boxes
Physical property Probe Measured quantity
mm µm nm pm fm <fm
Length scales of physical properties and measurements
Your measurement method
Lunds universitet / Fysiska institutionen / Fysikexperiment i forskning och samhälle FYSN11, HT 2009
Rutherford scattering
http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/ruther14.swf
Lunds universitet / Fysiska institutionen / Fysikexperiment i forskning och samhälle FYSN11, HT 2009
Characteristics of a physics experiment
•Control over cause – action•Controlled conditions: Control of as many parameters as
possible – systematic change of parameters • Idealisation / Abstraction•Reproducibility•Fundament in theory and/or model•Deliberate perturbation of a system in order to determine
the system’s characteristics
Rutherford scattering vs Characteristics of physics experiments
To what extent do these apply to the Rutherford scattering experiment?
Lunds universitet / Fysiska institutionen / Fysikexperiment i forskning och samhälle FYSN11, HT 2009
Probes
In Out
In
Out
Lunds universitet / Fysiska institutionen / Fysikexperiment i forskning och samhälle FYSN11, HT 2009
Probes
In Out
Photons / Electromagnetic fieldsElectrons
AtomsIons
NeutronsProtonsPositrons
AntiprotonsMuonsPions
Neutrinos...
Lunds universitet / Fysiska institutionen / Fysikexperiment i forskning och samhälle FYSN11, HT 2009
Choice of probe
Determination of the properties: disturb by suitabe radiation
• Choose wavelength according to probed interaction
• Penetrate into (or emit from) interior or surface only?
• If you want to receive information on length scales:de Broglie wavelength = h/p of same order as (or smaller than) the structure studied
• Smaller structures … higher momentum … bigger machines
Characterisation of a piece of matter: which properties are you interested in?
Lunds universitet / Fysiska institutionen / Fysikexperiment i forskning och samhälle FYSN11, HT 2009
de Broglie wavelengths
Wave-length
P=Ek if photon Ek if electr. Ek if p/n
10-9m(10-10m)
1.2keV/c (12keV/c)
1.4eV(140eV)
Thermal
10-12m 1.2MeV/c 0.79MeV 0.76keV
10-15m 1.2GeV/c 1.2GeV 0.59GeV
10-18m 1.2TeV/c 1.2TeV 1.2TeV
Lunds universitet / Fysiska institutionen / Fysikexperiment i forskning och samhälle FYSN11, HT 2009
Common concepts in experimental Physics
Each group picks a concept from the list below. During the lectures the group identifies how this concept was relevant in the type of experimental studies that was covered in the lecture.
You write a small essay about your concept in relation to the experimental physics you learn bout in the lectures. 2 pages written text plus figures.A preliminary writeup is delivered before the two last lectures. It is peer reviewed by your fellow who give feedbacktogether with one teacher. You respond to the criticism by correcting your text and include the two last lectures. Writing is individual, analysing the concept vs study material may be collaborative
•Concepts other years:
•Elastic scattering•Inelastic scattering•Energy levels•Conservation rules (energy, momentum, charge..)•Timing•Excitation•Quantal effects•crossections
Lunds universitet / Fysiska institutionen / Fysikexperiment i forskning och samhälle FYSN11, HT 2009
Examples of spectroscopic measurements
What do the following terms mean?
Spectrum – Spectroscopy
Where have you previously encountered these terms?
Lunds universitet / Fysiska institutionen / Fysikexperiment i forskning och samhälle FYSN11, HT 2009
Examples of spectroscopic measurements
Spectrum = lat. apparition, appearance
Came into use in the 17thcentury for describingwhat is seen when light isshone through a prism
www.wikipedia.org
Lunds universitet / Fysiska institutionen / Fysikexperiment i forskning och samhälle FYSN11, HT 2009
Examples of spectroscopic measurements
X-rayphotoelectronspectroscopy
X-ray absorptionspectroscopy
Time-dependentx-ray photoelectronspectroscopy
Lunds universitet / Fysiska institutionen / Fysikexperiment i forskning och samhälle FYSN11, HT 2009
Nuclear probe onmeteorite, x-rays
Examples of spectroscopic measurements
Almost Rutherford
Gamma energies from 61Zn 40Ca + 24Mg → 61Zn +p+p+n+γ
Lunds universitet / Fysiska institutionen / Fysikexperiment i forskning och samhälle FYSN11, HT 2009
Particle spectroscopyat high energy
Examples of spectroscopic measurements
HEP: often PT instead of kinetic energyEarly results from LHC (CMS exp)
Masses are the quantal states
Lunds universitet / Fysiska institutionen / Fysikexperiment i forskning och samhälle FYSN11, HT 2009
Writing articles about physics
• Any text about physics should be properly referenced.
• You may quote other sources. But remember:Quotes must be marked clearly.You must always provide the reference of the source (even for internet texts!).Only an insignificant fraction of your text may be composed of literal quotes (i.e., no ”cut and paste”).
• Enough information should be provided that a reader can repeat the experiment