Week 1 - Introduction Flashcards
All particles must obey the conservation law, what are they?
Charge (Q), Baryon Number (B), Lepton Number (L), Strangeness (S), Mass-energy & Momentum must all be conserved.
Exceptions:
• (S) doesn’t need to be conserved in weak interactions
• Quantum numbers can only take discrete numbers
What is the family tree of the particle?
Particle - 1. Lepton & 2. Hadrons
• Leptons - electron, muon, neutrino
• Hadrons - 2.1 mesons & 2.2 baryons
•• Mesons - pion & kaon
•• Baryons - proton & neutron
What is the definition of electron volt, eV? Units, conversion factors etc
Def: “a unit of energy equal to the work done on an electron in accelerating it through a potential difference of 1 volt”
1eV = 1.602 E-19 (C) x 1 (V) = J (kgm^2s^-2)
1MeV = 1.602 x 10^-13 J
Definition of energy, work and the SI units
Energy Def: “the capacity of doing work”
Work Def: “measure of energy transfer when an object is moved over a distance by an external force”
1 J = 1kg•m^2•s^-2
Work = Force x Distance = N•m
Size of the nucleus compared to size of the atom, what is the density of the nucleus?
Nucleus 10,000x smaller than the atom (approx)
Atom ~ 10^-10m
Nucleus ~ 10^-15m
Nucleus density = 2.3E10^27 kg•m^-3
Nucleus density, rho = 3•mass/(4•pi•r0^3)
Hence the nucleus density is constant
What is Relative Atomic Mass (RAM), what is 1 amu in kg and in MeV?
RAM Def: “the average mass of one molecule of a substance when compared with 1/12th of the mass of an atom of C-12”
1 amu = 1/12th the mass of C-12
= 1.661x10^-27 kg
= 931.5 MeV
1MeV = 1.602x10^-13 J
What is Avogadros number, the mole and it’s relation to the atomic masses and mass numbers?
Avogadro, N0: “the number of entities in a mole of a substance”
N0 = 6.022x10^23
Mole: “one mole is the amount of substance that corresponds to the number of atoms in 12g of C-12”
Mass number — Avg mass of an atom, taking into account all its naturally occurring isotopes.
Atomic number (A) is close to its mass number, hence if you one mole of a substance you will have A (atomic mass) grams of that material
What is Nuclear Binding energy, mass defect & Einstein’s mass-energy equivalence?
Mass Defect: “difference in mass of the actual atom and the sun of its constituent parts”
Binding Energy is equal to the mass_defect•c^2. Hence it’s the energy converted from the mass lost due to fission or fusion of particles.
Any reaction that includes a change in energy must be accompanied by a change in mass.
Nuclear stability and binding energy per nucleon
Inside the nucleus the forces are balanced, if we tried to move the nucleons apart, we would have to apply a force and do work. Likewise if we are pushing nucleons together. This energy is the binding energy.
BE/nucleon dictates the stability of a nucleus, the higher this value for the more stable it is. Fe-46 is the most stable element, elements to the RIGHT under FISSION and elements to the LEFT undergo FUSION to become more stable.
What does a negative binding energy suggest?
This would indicate the that the system is in an unbound state.
A nucleus is considered unbound when the protons and neutrons within it so not have enough binding energy to the hold the nucleus together
What is the definition of a nuclide? How does it differ to an isotope?
Nuclide: specific type of ‘atom’ characterised by the number of protons and neutrons in its nucleus.
Atom: is a basic unit of matter
Nuclide and isotope are the same thing
Isotope is used in relation to an element I.e. deuterium is an isotope oh hydrogen as opposed to deuterium and carbon-12 are nuclides
