Particles and Radiation Flashcards
what is the charge and mass of a proton?
+1.6x10^-19 and 1.67x10^-27
what is the charge and mass of a neutron?
0 and 1.67x10^-27
what is the charge and mass of an electron?
-1.6x10^-19 and 9.11x10^-31
what is specific charge and how do you calculate it?
it is the ratio of an atoms charge to its mass specific charge = charge/mass
What is an isotope?
Atoms of the same element that have different numbers of neutrons
what does electromagnetic force do in the nucleus?
causes the positively charged protons in the nucleus to repel each other
what does gravitational force do in the nucleus?
causes all the nucleons in the nucleus to attract each other due to their mass
what force stops the electromagnetic force tearing the nucleus apart?
strong nuclear force
what is the range of strong nuclear force?
it can hold nucleons together when they are separated by up to about 3fm(x10^-15)
why is the strong nuclear force repulsive up to about 0.5fm(x10^-15)?
otherwise there would be nothing to stop it crushing the nucleons to a point
what can you say about the size of the strong nuclear force whether it’s p-p, n-n or n-p?
it is the same as it works equally between all nucleons
how were neutrinos discovered?
it was observed that energy after beta decay was less than before, conservation of energy means a particle is responsible for making up the rest of the energy and momentum - the neutrino
what are the 7 types of EM radiation and how do wavelength and frequency change along the spectrum?
radiowaves, microwaves, infra-red, visible light, ultra-violet, x-rays, gamma rays. frequency increases down the spectrum, wavelength decreases
what is the relationship between the frequency and energy of a wave?
the higher the frequency the greater its energy
what is a photon and the equation of calculating their energy?
they are discrete waves (packets which carry energy) energy = (h x C)/wavelength
what is an anti-particle?
a particle which has the same mass and rest energy but opposite charge to it’s other in the particle - antiparticle pair
what can you assume about the rest energy of a neutrino and why?
that it is 0 because their mass is so small
what is pair production and what is required for it to happen?
when energy is converted into mass you get equal amounts of matter and anti-matter (this is pair production), it only happens if there is enough energy to produce the masses of the particles
in pair production why would the two particles produced curve away from each other in an applied magnetic field?
because they have opposite charges
what is the minimum energy needed for pair production?
it is the total rest energy of the particles produced (Emin=2E0)
what happens when a practice meets its antiparticle?
the annihilate, all mass is converted back to energy in the form of two gamma ray photons (2Ephotons=2E0)
how is annihilation used in industry?
in PET scanners - positron emitting isotope put it into the bloodstream and gamma rays produced are detected
what are hadrons and what are the 2 types?
they are non-fundamental particles which can feel the strong nuclear force. they are split into baryons and mesons
what are baryons (with examples) and what do they all decay into and why?
all baryons are made up of three quarks, for example protons and neutrons. all baryons eventually decay into protons because a free proton is not unstable
what are mesons and what are the 2 main types?
all mesons are made up of 2 quarks and are unstable, the two main types are pions and kaons
what are pions and kaons and name some properties?
pions are the lightest mesons and are the exchange particle of strong nuclear force.
kaons are heavier and more unstable, they have a very short lifetime and decay into pions
how can you detect mesons using cosmic rays?
cosmic rays interact with molecules in atmosphere and produce ‘showers’ of high-energy particles (including pions and kaons), they can be detected using 2 Geiger counters separated by absorbing lead. if both counters detect radiation simultaneously then it is likely that’s a ‘shower’
what are leptons?
fundamental particles which don’t feel the strong nuclear force, mainly interact through weak interaction but also a little through gravitational and electromagnetic
what are the 4 main types of lepton?
electrons, muons, electron neutrinos and muon neutrinos (muons are like heavier, unstable, electrons and decay eventually into electrons)
what 2 lepton quantities need to be conserved in reactions?
Le - electron lepton number
Lu - muon lepton number
how is strangeness created?
via the strong interaction and strange particles are created in pairs (to conserve strangeness)
how do strange particles decay and what happens to strangeness?
through the weak interaction and strangeness in not conserved
what properties are conserved in an interaction excluding the quantum numbers?
energy, momentum and charge
what are the properties on an up and anti-up quark?
up: charge = +2/3 baryon number = +1/3 strangeness = 0
anti-up: charge = -2/3 baryon number = -1/3 strangeness = 0
what are the properties of a down and anti-down quark?
down: charge = -1/3 baryon number = +1/3 strangeness = 0
anti-down: charge = +1/3 baryon number = -1/3 strangeness = 0
what are the properties of a strange and anti-strange quark?
strange: charge = -1/3 baryon number = +1/3 strangeness = -1
anti-strange: charge = +1/3 baryon number = -1/3 strangeness = 1
what are the quark compositions of the 4 types of kaon?
K+ = us-, K- = su-, K0 = ds-, K0- = sd-
what are the quark compositions of the 3 types of pion?
pi+ = ud-, pi- = du-, pi0 = uu-, dd- or ss-
what are the quark compositions of a proton or a neutron?
proton = uud, neutron = udd
why can you not get a quark by itself?
its just not possible, if you fire lots of energy at a proton the energy builds up until there is enough to make an u and u- couple and make a pi0
in decay what is the only interaction which can make quarks change type?
weak interaction
what are exchange particles?
virtual particles which are responsible for how forces act between two particles
what is the exchange particle of the strong nuclear force and what does it affect?
gluon/pions (all types) and they only effect hadrons
what is the exchange particle for the electromagnetic interaction and what does it affect?
virtual photon and it only effects charged particles only
what is the exchange particle or the weak interaction and what does it affect?
W+ and W- bosons and they affect everything
what 2 interactions do you need to do Feynman diagrams for?
weak and electromagnetic
what are the 4 things you need to know about Feynman diagrams?
incoming particles start at the bottom
baryons stay on one side, leptons on the other
W bosons carry charge between sides (to balance charge)
a W- going left is the same as a W+ going right
what is the Feynman diagram for beta-minus decay?
Vertical line with n below and p above
Squiggly line coming off diagonal (W-)
Above line departing off (v with minus above)
Below is e-
what is the Feynman diagram for beta-plus decay?
vertical line with p below and n above
Squiggly line coming off diagonal (W+)
Above line departing off (v)
Below is e+
what is the Feynman diagram for electron capture?
P going diagonal, n breaking off that
Squiggly line in middle (w+) Arrow above going right.
V breaking off above
e- breaking off below
what is the Feynman diagram for an electron - proton collision?
P going diagonal, n breaking off that
Squiggly line in middle (w-) Arrow above going left
V breaking off above
e- breaking off below
what is the Feynman diagram for electromagnetic repulsion?
e- going diagonal, e- breaking off that
Super Squiggly line in middle with fancy Y
e- breaking off above
e- breaking off below
