3.2 Particles and Radiation Flashcards
What is the type of metre do we measure an atom’s nucleus’ diameter in?
Femtometres.
What type of metre do we measure the atomic diameter in?
Picometers.
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 does Q stand for in Q/m?
Charge.
What does m stand for in Q/m?
Mass.
What is a nucleon?
A particle in the nucleus.
Define isotopes.
Versions of the same element, they have the same proton number but different mass (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.
How far does the strong nuclear force stretch up to?
~ 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, how short a range and why does it do this?
Becomes a repulsive force, 0.5fm, to stop the nucleus from collapsing in on itself.
What is an alpha particle made up of?
2 protons, 2 neutrons.
What is an alpha particle represented by?
α
What is an alpha particle the same as?
A helium nucleus.
Rank the speeds of alpha, gamma, beta from slowest to fastest.
Alpha, beta, gamma.
What is the charge of an alpha, what does this mean the particle is?
2+, strongly ionising.
What is a beta particle?
1 electron.
How do we represent beta, where does it occur?
β, neutron rich nuclei.
What is the charge of beta, what does this mean the particle is?
-1, weakly ionising.
What do we write for beta’s atomic/proton number?
-1.
How does a beta 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 + (anti)Ve
In alpha decay X -> ? + ?.
Y + α.
What is the mass number (A) and proton number (Z) of α?
A = 4, Z = 2.
In beta decay X -> ? + ? + ?
Y + β + (anti)Ve
What is the mass number (A) and proton number (Z) of β?
A = 0, Z = -1.
Which type of decay happens in large, heavy nuclei?
α.
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 opposing.
1eV = how many J?
1.60x10^-19
How many eVs are in 1MeV?
1 million.
Rest energy is the energy equivalent to what?
Rest mass (when converted into energy).
Energy = ??
hf
What is h?
The plank constant.
What is f?
Frequency of a light wave.
Light waves can be considered to be a stream of what?
‘Discrete’ packets of energy called photons.
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 order of the visible light spectrum?
ROYGBIV
What on the EM spectrum has the lowest frequency?
Radio waves.
Wavelength can be represented as what?
λ.
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 = ??
mv
What can a gamma photon spontaneously do and where does it does this?
Convert its energy into mass in the form of a particle-antiparticle pair, usually 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 four fundamental interactions?
Strong nuclear (or strong interaction), weak nuclear, electromagnetic (including electrostatic), gravity.
What is another name for exchange particles?
Gauge bosons.
What are the exchange particles for strong nuclear force?
Pion, π+, π-, π0.
What are the exchange particles for weak nuclear force?
Bosons, W+ and 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.
The smaller the mass of the exchange particle the…?
Greater the range of the force.
When drawing a representation of particles repelling using people, what are the people doing?
Person 1 throws a ball, recoils, then person 2 gets hit by the ball and recoils.
When drawing a representation of particles attracting using people, what are the people doing?
Person 1 throws a boomerang away from person 2, person 1 recoils, boomerang hits person 2, they recoil.
Can exchange particles be overcome by more of a different exchange particle? If so give an example of this.
Yes, eg in a nucleus pions can attract more than virtual photons repel (not always).
What’s the symbol for an antineutrino?
νe, with a bar over it.
In a Feynman diagram what is usually on the left and what is usually on the right?
Left is baryons, right is leptons.
In a Feynman diagram what increases as in diagram from bottom to top?
Time.
What is the wiggly line on a Feynman diagram?
The exchange particle.
What is always conserved at the junctions in a Feynman diagram?
Charge, baryon and lepton numbers.
In a Feynman diagram does it matter if the arrow for the exchange particle is on the left or right?
No.
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 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 collide (duh).
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?
Baryons, antibaryons, mesons.
Name the baryons.
Proton (p) and neutron (n).
What are baryons made up of?
3 quarks.
What are the baryon numbers for protons and neutrons?
B = +1.
Name the antibaryons.
Antiproton (bar over p) and antineutron (bar over n).
What are the antibaryons made up of?
3 antiquarks.
What are the baryon numbers for antiprotons and antineutrons?
B = -1.
What is special about the pion?
It’s the exchange particle for strong nuclear force.
What are the mesons?
Pion and kaon.
What are the types of pion?
π+, π-, π0.
What are the types of kaon?
K+, K-, K0, K0(with a bar).
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 (think beta- decay).
What is the baryon number all of mesons?
B = 0, they aren’t baryons.
What always happens to the baryon and lepton number?
It gets conserved.
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).
Should the two types of lepton number be considered differently?
Yes.
What is the Le of an electron and electron neutrino?
+1.
What is the Le of a positron and an electron antineutrino?
-1.
What is the Lμ of a muon and muon neutrino?
+1.
What is the Lμ of an antimuon and muon antineutrino?
-1.
Electrons are what?
Stable and do not decay.
A muon decays into what?
An electron.
What are leptons not involved with?
Strange particles.
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.
What can weak interactions change strangeness by?
0 (no change), +1 or -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 (u), down (d), strange (s).
