2- Chapter 17 - Matter Flashcards
What is a positron?
Antimatter/Antiparticle fr an electron with the same mass but opposite charge.
What happens when an antimatter meets its mirroring matter?
They both annihilate and release 2 gamma rays witch total energy mc2
The two gamma rays have equal energy and travel opposite directions
What is the direction in a feynman diagram?
Bottom to top
Whats the symbol for a photon in a feynman diagram?
A wavey live with a arrow at the end.
Symbol for a gluon on a feynman diagram
a spring with an arrow at the end.
What are fermions?
- Eg electrons
- Only one per energy state
- HAve quantised amounts of spin
- Phases add up with opposite phase so if two identical met youd have 0 amplitude
What are bosons?
- eg photons
- like to be in the same state
- Phases add when together
- Are exchanged in interactions
How can matter be created
A gamma ray with energy > 2mc2 passes by a neuclus and releases a positrona nd electron
What is a neutrino?
Small, massless , Chargeless - no interaction with matter
They account for uneven beta decay
How does uneven beta decay happen
a neutrino of random energy is released and is invisible.
THis means the electron wil have a random energy and random path length
What are baryons?
Heavy particles eg proton and neuton
What are leptons?
light particles eg electron , (electron) neutrino
Equation for the beta decay of Strontium
What is the weak interaction?
the exchange of the bosons Z0 (neural) , W+ and W-
A neutron can change into a protom by emmiting a W- boson (which decays into an electron and anti neutrino)
What does alpha scattering in gold show?
SHows that a charged neuclues must exist, and that its positive.
WHat is the charge of an Up quark?
+2/3e
What is the charge of a down quark?
-1/3e
What is a proton made of?
uud
What is a neutron made of?
udd
Quark combination rules?
- must combine to be colourless
- This can happen in trios to create a baryon
- Or in pair to create a meson
What is a gluon?
Holds quarks together thought energy/colour exchange
How the the force of a gluon change
it increases as you pull the quarks further apart
what does a red/blue gluon do?
swaps a red and a blue quarks colour around
whats different about an antimatter?
has opposite charge,lepton and baryon number , colour
what causes electromagnetic interactions?
the exchange of photons
En is proportional to
-1/n2
what is a continuous spectrum?
- From incandescent light
- all colours with no gaps
- the hotter the body the more blue/violet the predominant colour is.
What is line emmision spectra?
typical of exited gasses
- only certain wavelegth are present
- different pattern for each element which appear as bright lines
What does the (atomic) hydrogen emmision spectr look like?
En For hydrogen =
-13.6eV x 1/n2
What explains the emmision spectra of hydrogen?
The first seris is from an electron terminating at level 1 whcih means that energy difference is higher and this explains the bunching of lines in the emission spectra.
What is a line absorbtion spectra?
What frequencies are absorbed by a object.
Its the same as the objects emmision spectra but with dark spons where the light spots freviously were.
(used in redshift)
Why is it -1/n2 in the emmision spectra?
as the charges are negative and get attracted to the positive neaclus
What is Eionise
0
Whats different about electron scattering?
very few go through large scattering angles and most pass stragight thoguh
How are volume and mass number related?
r=r0A1/3
Volume is proportional to mass number
What happens when you poull two quarks further apart
the force holding them together by the gluon gets stronger and stogner until new matter is created usually as a meson.
de broglie wavelength=
h/p
quantum jumps in energy level
E=hf=Einitial-EFinal
three generations of fundamental particles?
- Electron, electron-neutrino Down,Up
- Muon, Muon-neutrino stange,charmed
- Tau,Tau-neutrino bottom,top
