Topic 6 Nuclei and Particles Flashcards
In what two ways can mass be formed?
- Photons can collide to form a matter-antimatter pair.
- Matter-antimatter particles can form spontaneously from nothing using “burrowed” energy. They only exist briefly and then disappear as the energy needs to be repaid.
Relationship between energy and time equation
delta E x delta t ~ h / 4pi
where h is Planck’s constant, delta E is the precise specification of energy and delta t is the time interval.
How much energy is required to form a particle?
The specific energy of the mass of the particle and antiparticle would be required to create the particle pair.
If an electron had an energy mass of 510 keV, the photons that create the electron-positron pair would require a minimum energy of 1020 keV (1.02 MeV).
What are the 3 rules of conservation for nuclear processes?
- Electric charge is conserved: the net charge of the products of a nuclear process is the same as the net charge of the original nucleus or nuclei.
- Mass number is conserved: the total number of nucleons in the products is the same as that in the original nucleus or nuclei.
- Energy is conserved: as it is in all physical processes.
What is mass defect?
The mass of any needs is less than the total mass of the individual nerdcons of which it is composed. The difference is referred to as the mass defect of the nucleus, usually expressed in units of MeV/c^2.
What is binding energy?
The energy released when a nucleus is formed from its constituent nucleons.
What is binding energy per nucleon?
The binding energy of a nucleus divided by the number of nucleons of which it is composed. The nuclide with the largest binding energy per nucleon is iron-56 with a value of 8.8 MeV.
What is an alpha particle?
A helium 4 nucleus comprising of 2 protons and 2 neutrons.
What is alpha decay?
A nuclear decay process in which a nuclide emits an alpha particle. The binding energy of the products is more than that of the parent nuclide.
234U92 > 230TH90 + 4He2
What is beta minus decay?
A type of nuclear decay in which a neutron is converted into a proton with the emission of an electron (e-) and an electron antineutrino (νe with line over).
At a deeper level this may be understood as resulting from the conversion of a down quark to on up quark. All beta decays are examples of processes that depend on weak interactions.
This occurs in nuclei that have too many neutrons to be stable..
214Pb82 > 214Bi83 + e- + νe (line over top)
What is a beta-particle?
An election (or sometimes positron) produced in beta decay.
What is beta plus decay?
A type of nuclear decay where a proton is converted into a neutron with the emission of a position and an election neutrino.
At a deeper level it may be understood as resulting from an up quark converting into a down quark. All beta decay are examples of processes that depend on weak interactions.
Occurs in nuclei that have too few neutrons to stable.
14O8 > 14N7 + e+ + νe
What is electron capture?
A type of radioactive decay in which an atomic nucleus with too many protons captures an electron. The effect is for one proton to turn into a neutron with the emission of on electron neutrino. The effect on the nucleus is the same as beta plus decay.
It occurs in Medea that have too few neutrons to be stable.
26Al13 + e- > 26Mg12 + νe
What is gamma decay?
A type of nuclear decay in which a nuclide in an excited state emits a gamma ray photon and so makes a transition to a lower energy level.
What are gamma rays?
Electromagnetic radiation corresponding to the highest energy photons, or equivalentlythe shortest wavelength and highest frequency radiation.
What is a parent isotope?
A radioactive isotope that undergoes radioactive decay whose products are referred to as daughter isotopes.
What are daughter isotopes?
An isotope formed as a result of a radioactive decay from a parent isotope.
Calculating how many parent isotopes are left after n halflives?
P = (1/2)^n Po
Where P is the number of parent isotopes at any time, n is the number of half lives and Po is the initial number of parent isotopes.
Alternative forms:
P / Po = (1/2)^n
Po = 2^n P
Calculating the age of rock using daughter / parent ratios.
D = Po - p
D = 2^n P - P
D / P = 2^n - 1
Where D is the number of daughter isotopes present, P is the number of parent isotopes present, n is the number of half lives and Po is the initial number of parent isotopes.
What is nuclear fission?
A proceeds by where a relatively large nucleus splits apart into two less massive nuclei of roughly equal size.
This may occur spontaneously or induced by bombarding the nucleus with other particles.
What is a lepton?
A fundamental particle, the matter counterpart of an antilepton. There are six flavours of lepton: the electron (e-), muon (μ-), tauon (τ-), electron neutrino (νe), muon neutrino (νμ) and tauon neutrino (ντ).
What is a quark?
A fundamental particle of matter, the matter counterpart of an antiquark. There are 6 flavours of quark: up (u), down (d), charm (c), strange (s), top (t), and bottom (b).
Quarks are found in baryons and mesons but never in isolation.
What is a muon?
A negativity charged fundamental particle (lepton) similar to an electron but with a mass about 200 heavier. Its antiparticle is called on antimuon.
This particle is unstable and rapidly decays to an electron.
What is a tauon?
A negativity charged fundamental particle (lepton) similar to an electron but with a mass about 3500 heavier. Its antiparticle is called on antitauon.
This particle is unstable and rapidly decays to an electron.
What is a muon neutrino?
A fundamental particle (a lepton) with zero electric charge. Its corresponding antimatter particle is called the muon antineutrino.
What is a tauon neutrino?
A fundamental particle (a lepton) with zero electric charge. Its antiparticle is called the tauon antineutrino.
What is a positron?
(antielectron) The antimatter counterpart to the electron. It has an electric charge of +e, but the same mass as the electron. It is produced in beta-plus decay processes.
What is an up quark?
(u) A type of quark - a fundamental particle with electric charge +2e/3. One of the constituent particles of both the proton and the neutron.
What is a down quark?
(d) A type of quark - a fundamental particle with electric charge –e/3. One of the constituent particles of both the proton and the neutron.
What is a charm quark?
(c) A type of quark - a fundamental particle with electric charge +2e/3.
What is a strange quark?
(s) A type of quark - a fundamental particle with electric charge –e/3.
What is a top quark?
(t) A type of quark - a fundamental particle with electric charge +2e/3. (The top quark is sometimes alternatively referred to as ‘truth’.)
What is a bottom quark?
(b) A type of quark - a fundamental particle with electric charge –e/3. (The bottom quark is sometimes alternatively referred to as ‘beauty’.)
Do quarks have antimatter counterparts?
Yes, and their symbols are the same with a line above them.
Which quarks are largest?
Up and down quarks are the smallest, charm and strange are more massive and top and bottom are more massive still.
What is a hadron?
A composite particle composed of quarks and/or antiquarks.
Baryons, antibaryons and meson are all hadrons.
What is a baryon?
A subatomic particle composed of three quarks, the matte companion of an antibaryon which are both hadrons.
Examples include protons and neutrons.
What is an antibaryon?
A subatomic particle composed of three antiquarks, the antimatter companion of an baryon which are both hadrons.
Examples include antiprotons and antineutrons.
What is a meson?
A subatomic particle composed of a quark and an antiquark. A type of hadron. Examples of mesons include the pions.
What are the three rules of conservation for high energy reactions?
- Energy is conserved.
-Electric charge is conserved - The number of quarks minus the number of antiquarks is conserved.
What is strong interaction?
This is the strong force that binds quarks together inside nucleons (protons and neutrons).
This force can leak out from the nucleon to create the force that binds protons and neutrons together.
What is a virtual photon?
A photon involved in carrying the electromagnetic force from one part of an interaction to another. Virtual photons do not escape from processes and are never detectable directly.
What is a gluon?
The quantum of energy associated with the strong interaction. It plays a role in QCD analogous to that of photons in QED. Unlike photons, gluons themselves experience the strong interaction (photons do not experience the electromagnetic interaction). This is because gluons possess colour charge. (Photons do not possess conventional electric charge.) Consequently, gluons have a very short range and are never observed in isolation.
These decay rapidly into quark-antiquark pairs.
What is quantum chromodynamics?
(QCD) The theory that describes the strong interaction. It explains these interactions as arising due to the exchange of gluons between particles that possess colour charge. Compare with quantum electrodynamics.
What is colour charge?
A property possessed by quarks (and antiquarks) and gluons. It plays a role in QCD equivalent to that of electric charge in QED. Quarks can possess any one of red, green or blue colour charge.
What colour charges must the particles in a baryon have?
There must be one red, green and blue on order to cancel each other out, leaving no colour overall.
What colour charges must particles in a meson have?
They must have opposite colour charges i.e. red + antired.
What is confinement?
This is the locking up of quarks inside hadrons.
What are weak interactions?
Fundamental interaction involving both quarks and leptons. One of the four fundamental interactions. It describes interactions between particles in terms of the exchange of quanta called W bosons and Z bosons. No structure’s bound together by a ‘weak force’. Weak interactions are responsible for processes such as beta-decay in which quarks change flavour and lepton–antilepton pairs are produced.
What is a boson?
A particle responsible for transmitting one of the four fundamental interactions, or one of the unified interactions. See also photon, gluon, W boson, Z boson, graviton, Higgs boson, X boson.
How are bosons related to beta minus decay?
A down quark decays into a W- boson and an up quark. The W- boson subsequently decays into an electron and an electron antineutrino.
What are the rules for all weak interactions?
- Electric charge is conserved.
-The number of quarks minus the number of antiquarks is conserved.
-The number of leptons minus the number of antileptons is conserved. - Flavour changing of the quarks to leptons is allowed, as long as these three rules are obeyed.
How is a W+ boson seen in a beta plus decay?
An up quark decays into a W+ boson and a down quark. The W+ boson subsequently decays into a positron and an electron neutrino.
How is a Z0 boson formed?
An electron–positron pair undergo annihilation, creating a Z0 boson which subsequently decays to create a muon neutrino and muon antineutrino pair.
Which particles carry a colour change?
Quarks and gluons.
Which particles are colour neutral?
Baryons, antibaryons and mesons are all colour neutral.
