Particle Physics Flashcards
How is specific charge calculated?
the overall charge of the atom/nucleus divided by the total mass of the atom/nucleus
(total protons x charge of a proton) / (total nucleons x mass of a nucleon)
NpQp/NnMn
What is the charge of a proton?
1.6x10^-19C
What is the charge of a neutron?
0C
What is the charge of an electron?
-1.6x10^-19
What is meant by the ‘rest mass’ of a particle?
the minimum mass of a particle is when it is at rest, hence this is the ‘rest mass’
What is the mass of a proton?
1.67x10-27kg
What is the mass of a neutron?
1.67x10-27kg
What is the mass of an electron?
9.11x10-31kg
Define nucleon number, and state which letter this is represented by.
the total number of protons and neutrons within the nucleus, A
Define proton number, and state which letter this is represented by.
the total number of protons in the nucleus or the total number of electrons orbiting the nucleus, Z
What is an Isotope?
an atom which contains the same number of protons and electrons as its element but has a different number of neutrons
What force holds together the nucleus of an atom and what is its attractive range?
Strong nuclear force, 3fm
What is the repulsive range of the strong nuclear force and why is this useful?
0.5fm, it prevents the nucleus from collapsing in on itself
What subatomic particles make up an alpha particle and state the charge of this particle?
2 protons and 2 neutrons (Helium nucleus), 2+ charge
What is the range of alpha radiation in air and what barrier can be used to stop it?
approx. 5cm, thin paper
When might a nucleus undergo alpha decay?
when its mass number is very large
Which particles are emitted during beta minus decay?
a fast moving electron and an antineutrino
What happens during beta minus decay?
a neutron turns into a proton and an electron and antineutrino are emitted.
Why do nuclei undergo beta minus decay?
the nucleus has too many neutrons
What is emitted during gamma decay?
a gamma photon
What happens during gamma decay?
EM radiation is emitted from the unstable nucleus in the form of a photon.
When do nuclei experience gamma decay?
when they have too much energy
What is a neutrino and why is it released during beta decay?
it was hypothesised this was to balance the conservation of energy. it also balances lepton number.
What is an antiparticle?
every particle has a corresponding antiparticle. It has the same mass and rest energy but an equal and opposite charge. it is made of antiquarks.
Which particles are released during beta plus decay?
positron and neutrino
What happens during beta plus decay?
a proton turns into a neutron and a positron and neutrino are released.
Why do nuclei experience beta plus decay?
if a nucleus is proton rich
What is the antiparticle of an electron?
positron
What is the antiparticle of a proton?
antiproton
What is the antiparticle of a neutron?
antineutron
What is annihilation?
when a particle and its antiparticle meet they are destroyed releasing a large amount of energy via photons. the amount of energy released is the rest energy of the particle/antiparticles.
What is pair production?
When a particle and its antiparticle are made, if there is enough energy absorbed by photons.
What is a photon?
a ‘packet’ of energy. it has no charge and no mass, each photon has its own discrete energy value dependent on its frequency.
What is a neutrino?
a particle with no charge and very small mass. it is not affected by electrostatic forces because they have no charge so they can pass through other particles without interacting. millions pass through the body every second.
How is the energy of a photon calculated?
E = hf
or
E=hc/wavelength
What is Planck’s constant?
h, 6.63x10^-34Js
What is the rest energy of a particle?
the amount of energy required to make a particle move. the amount of energy release in annihilation
Which particle carries the gravity force?
graviton?
Which particles carry the weak force?
W+, W-, Zo
Which particles carry the EM force?
photons
Which particles carry the strong force?
Gluon
What particles does the gravity force act on?
all
What particles does the weak force act on?
quarks, leptons
What particles does the EM force act on?
quarks, leptons, W+, W-
What particles does the strong force act on?
quarks, gluons
What is the weak nuclear force responsible for?
radioactive decay of subatomic particles
What is the electromagnetic force?
the force between two charged objects, due to the exchange of virtual photons
What are the different flavours of quarks (in their pairs)?
Up and down
top and bottom
strange and charm
What is the quark structure of a proton?
uud
What is the quark structure of a neutron?
udd
What is a baryon made up of?
3 quarks
What is an antibaryon made up of?
3 antiquarks
What is a meson made up of?
a quark and an antiquark pair
What are the properties of a hadron?
Heavy and massive
not fundamental so can be split up
What force do hadrons experience?
strong
What force is responsible for the decay of hadrons?
weak
If a hadron has protons involved in its decay, what is it?
baryon
If a hadron does not have protons involved in its decay, what is it?
meson
What are the properties of a lepton?
light and small
fundamental
What forces do leptons interact via?
if charged, EM or weak
Which particles are baryons?
protons, neutrons
Which particles are mesons?
pions, kaons
What force do mesons carry?
strong
What is the only stable baryon?
proton
What must be conserved for a nuclear reaction to occur?
charge, Q
lepton number, L
baryon number, B
(strangeness, S)
When is strangeness conserved?
during strong and EM but not weak interactions.
Why is strangeness not conserved during weak interaction?
lighter particles containing strange quarks cannot decay via strong so must decay via weak.
What is an exchange particle?
Exchange or virtual particles interact with particles to produce the effects of attraction or repulsion. They do this by shuttling back and forth between the particles, carrying small packets of energy.
What happens during electron capture?
an electron in an atom’s inner shell is drawn into the nucleus where it combines with a proton, forming a neutron and a neutrino. The neutrino is ejected from the atom’s nucleus.
What type of interaction is electron capture?
weak
Which exchange particle is present in electron capture?
W+
Which exchange particle is present in strong nuclear ineractions?
pion
Which particle will decay into a pion?
kaon
Which particle does a muon decay into?
electron
Define strange particles.
Strange particles are particles that are produced through the strong interaction and decay through the weak interaction. (eg kaons).
What are strange particles always created as?
pairs
What does particle physics rely on?
the collaborative efforts of large teams of scientists and engineers to validate new knowledge
Which two factors are always conserved?
energy and momentum
