Particles Flashcards
What are the three constituents of an atom? (3)
Proton, Neutron, Electron
What is the relative mass of a Proton?
1
What is the relative mass of a Neutron?
1
What is the relative mass of an Electron?
1/1830
What are the units for Specific Charge?
CKg-1
What is the equation for Specific Charge?
Q/m
What is a Nucleon?
A particle in the nucleus
What are Isotopes?
Versions of the same element, they have the same proton number but different number of neutrons
What is another name for the Mass Number?
Nucleon number
What is another name for the Proton Number?
Atomic number
What is the Strong Nuclear Force?
An attractive force between nucleons
What is the range of the Strong Nuclear Force?
~ 3 fm
What does Strong Nuclear force do in an atom?
Overcomes the repulsion between positive protons and holds the nucleus together
What does the strong nuclear force do at short ranges?
Becomes a repulsive force
At what range does strong nuclear force become repulsive?
~ 0.5 fm
Why does the strong nuclear force become repulsive at close range?
To stop the nucleus from collapsing in on itself
What is an alpha particle made up of? (2)
2 Protons, 2 Neutrons
What is an Alpha Particle the same as?
A helium nucleus
How fast is an Alpha compared to Gamma and beta?
Slowest
What is the charge of an Alpha Particle?
2+
What does the 2+ charge mean an Alpha is?
Strongly ionising
What is a Beta Particle?
1 electron
How fast is Beta compared to Alpha and Gamma?
Faster not fastest
What is the charge of a Beta Particle?
-1
What do we write for Beta’s atomic/proton number?
-1
What does the -1 charge mean a Beta Particle is?
Weakly ionising
How does a Beta Particle ionise?
By pushing/repelling electrons off atoms
How is a Beta Particle created?
A neutron turns into a proton and an electron (beta)
n -> ? + ?
p + β
Where does Beta Decay occur?
Proton rich nuclei
Where does Alpha Decay occur?
Large Nuclei
Which type of decay happens in neutron-rich nuclei?
β-, neutron emitter
Which type of decay happens in proton-rich nuclei?
β+, electron capture
How are Alpha Particles emitted from the nucleus?
The repelling of the other protons overcomes the strong nuclear force and pushes it out
In a Cloud Chamber what qualities do Alpha trails share, and why?
Length, because all alpha have the same kinetic energy
For Beta trails, do they share length, and why?
They don’t share length, they have varying kinetic energy, but the parent nucleus still loses the same energy
What explains the extra energy lost in Beta Decay?
The antineutrino
What qualities do corresponding Particles and Antiparticles share?
Rest mass and rest energy
What qualities do corresponding Particles and Antiparticles do not share?
Charge, baryon, lepton and strangeness numbers are opposite
What is an electron volt (eV)?
The work done by an electric field when accelerating an electron through a potential difference of 1 volt
Is an eV big or small?
Small
How many eVs are in 1MeV?
1 million
Rest energy is the energy equivalent to what?
Rest mass (when converted into energy)
What is the Electromagnetic Spectrum in order?
Radio, Microwave, Infrared, Visible, Ultraviolet, X-ray, Gamma ray
What is the longest wave length in the EM spectrum?
Radio
What is the shortest wavelength in the EM spectrum?
Gamma ray
What on the EM spectrum has the lowest frequency?
Radio waves
What on the EM spectrum has the highest frequency?
Gamma rays
Speed of light in a vacuum?
300 x 10^8 ms^-1
What happens in Pair Production?
Energy is converted into mass in the form of a particle-antiparticle pair
Where does the energy come from in Pair Production?
A collision or gamma photon
p (momentum) = ?
m (mass) x v (velocity)
What can a Gamma Photon spontaneously do and where does this occur?
Convert its energy into mass in the form of a particle-antiparticle pair. Usually happens near a nucleus which then recoils to conserve momentum
What is Annihilation?
Where a particle meets its antiparticle counterpart and they convert their mass into energy into the form of a pair of gamma photons
What are the 4 fundamental interactions?
Strong nuclear (or strong interaction), weak nuclear, electromagnetic (including electrostatic), gravity
What are the Exchange Particles for Strong Nuclear Force?
Pions
What are the Exchange Particles for Weak Nuclear Force?
Bosons W+ W-
What are the Exchange Particles for Electromagnetic Force?
Virtual photon
What is the Exchange Particle for Gravity?
Graviton
What do Exchange Particles do?
Pass between particles to carry the force, energy, charge and momentum across
What is the Exchange Particle when a Proton and an Electron are attracted to each other?
Virtual photon
The smaller the mass of the Exchange Particle the…?
Greater the range of the force
Can Exchange Particles be overcome by more of a different exchange particle? If so give an example of this
Yes, e.g. in a nucleus pions can attract more than virtual photons repel (not always)
What is the equation for beta- decay?
n -> p + β- + (anti)νe
In a Feynman diagram what is usually on the left and what is usually on the right?
Left is baryons, right is leptons
What is always conserved at the junctions in a Feynman diagram?
Charge, baryon and lepton numbers
In a Feynman diagram for beta- decay what goes into and what comes out of the first junction? And what direction does the exchange particle go in?
Neutron goes in, proton and W- exchange particle goes out. W- to the right
In a Feynman diagram for beta- decay what goes into and what comes out of the second junction?
W- exchange particle goes in, β- and a (anti)νe (antineutrino) comes out
What is the equation for β+ decay?
p -> n + β+ νe
In what sort of nucleus does beta+ decay occur?
Proton-rich
In a Feynman diagram for beta+ decay what goes into and what comes out of the first junction?
Proton goes in, neutron and W+ exchange particle comes out
In a Feynman diagram for beta+ decay what goes into and what comes out of the second junction?
W+ exchange particle goes in, β+ and νe comes out
What happens in Electron-capture?
An inner shell electron is captured by a proton in the nucleus (becoming a neutron)
What is the equation for Electron-capture?
p + e- -> n + νe
In what sort of nucleus does Electron capture occur?
Proton-rich
In a Feynman diagram for electron capture what goes into and what comes out of the first junction? And what direction is the exchange particle in?
Proton goes in, neutron and W+ exchange particle comes out. W+ to the right
In a Feynman diagram for electron capture what goes into and what comes out of the second junction?
W+ exchange particle and e- goes in, νe comes out
W+ to the right is the same of what?
W- to the left
What happens in proton-electron collision?
A proton and electron colide
What sort of nucleus does proton-electron collision happen in?
A stable one
The Feynman diagram for proton-electron collision is the same as what?
Electron capture
What is a hadron and what are they composed of?
They are composed of quarks and antiquarks, they experience the strong interaction/ strong nuclear force
What are the types of hadron? (3)
Baryons, antibaryons, mesons
Name the baryons
Protons and neutrons
What are baryons made up of?
3 quarks
What are the baryon numbers for protons and neutrons?
+1
What are the Antibaryons? (2)
Antiproton antineutron
What are the antibaryons made up of?
3 antiquarks
What are the baryon numbers for antiprotons and antineutrons?
-1
What are the mesons?
Pions and kaons
What are mesons made up of?
A quark and antiquark pair
What is special about a proton?
It’s the only stable baryon into which other baryons eventually decay
What is the baryon number all of mesons?
B = 0, they aren’t baryons
What can a kaon do?
Decay into a pion
What is a kaon?
A strange particle
What is a lepton?
A particle that doesn’t experience the strong interaction/ strong nuclear force
What are the leptons that aren’t neutrinos?
Electron (e-), positron (e+), muon (μ-) and antimuon (μ+)
What are the leptons that are neutrinos?
Electron neutrino (νe), electron antineutrino (νe, with a bar), muon neutrino (νμ), muon antineutrino (νμ, with a bar)
What are the two types of lepton number?
Electron lepton number (Le) and muon lepton number (Lμ)
What is the Le of an electron?
+1
What is the Le of a positron?
-1
What is the Le of a muon and antimuon?
0, not electron leptons
What is the Lμ of an electron and positron?
0, not muon leptons
What is the Lμ of a muon?
+1
What is the Lμ of an antimuon?
-1
What is the Le of an electron neutrino?
+1
What is the Le of an electron antineutrino?
-1
What is the Le of a muon neutrino and an antimuon neutrino?
0
What is the Lμ of an electron neutrino and an electron antineutrino?
0
What is the Lμ of a muon neutrino?
+1
What is the Lμ of a muon antineutrino?
-1
What is the Le and Lμ of hadrons?
0
What does a muon decay into?
An electron
What do strange particles contain?
Strange or antistrange quarks
What type of particle are strange particles?
Hadrons
Strange particles are produced in what?
Strong interactions
Strange particles decay via what?
Weak interactions
Strong interactions must conserve what?
Strangeness
Strange particles are always produced in what, why?
Pairs of s=+1 and s=-1, because strangeness is always conserved in strong interactions
Do weak interactions have to conserve strangeness?
No. Can change by +1 -1
What is the strangeness of a K+ and K0 particle?
+1
What is the strangeness of a K- and a K0(with a bar)?
-1
What are the types of quark?
Up, down, strange
What are the charges a quark can have?
Q(charge) = +2/3e (+2/3 of an electron) or Q = -1/3 (-1/3 of an electron)
