P1: Matter and Radiation Flashcards
Decay, categories of subatomic particles, interactions, radioactivity
What is electron capture?
When a proton from a proton-rich nucleus interacts with an inner shell electron through the weak interaction, turning into a neutron using a W-boson.
The electron is turned into a neutrino.
(can also happen when an electron and proton collide at high speeds).
The weak force
- A force weaker than the strong force, enacted by the W-boson.
- It occurs in the weak interaction and in beta decay.
- Affects all types of particles, when quark structure changes
Characteristics of a W+/W- boson
- have a non-zero mass
- have a range of no more that 0.001fm (very short with a very short half life too)
- can be positively or negatively charged
- are leptons
W bosons in beta decay
What does a W+/W- boson do?
A W- boson decays into a B- particle and an antineutrino.
A W+ boson decays into a B+ particle and a neutrino.
The 4 fundamental forces
+ a bit about each one
Electromagnetic: the force between any two charged objects, exerted by the virtual photon.
Strong Nuclear: the force holding the nucleus together, enacted by the gluon/pion.
Weak: force felt by any particle, exerted by W bosons.
Gravitational: enacted by the gravitron (in theory) on any particle with mass.
What must be conserved during any particle interaction?
- Lepton number
- Baryon number
- Charge
- Strangeness (but not important for weak interactions)
- Energy
- Momentum
Specific charge
= charge / mass (meaured in C/kg)
About the strong force… (Give at least 1 point out of 4)
- Its range is no more than about 3-4 fm (x10^-15 m) which is about the same as the diameter of a small nucleus
- It has the same effect between 2 protons as it does between a proton and a neutron or between 2 neutrons
- At separations less than 0.5fm, it is repulsive, in order to stop nuclear components from colliding with each other
- It counteracts the electrostatic repulsion between protons
Specific Charge of a Proton?
charge/mass = 9.58 x 10^7
State a use of radioactive isotopes
Carbon Dating: the proportion of carbon-14 in a material tells us it approximate age.
What makes a nucleus unstable?
Having too many protons and/or neutrons.
What kind of decay takes place when an atom has too many nucleons?
Alpha decay (-2 protons -2 neutrons from the nucleus)
Decaying when there are too many neutrons in an atom is..?
And say what change occurs (+1)
Beta decay (neutron decays to a proton; udd into uud) by the weak interaction
How was the neutrino’s existence hypothesised?
During beta decay a particle with 0 charge and negligible mass must have been emitted to account for the energy lost.
Antiparticles
Are particles with the same rest energy and mass but with other qualities completely opposite to each other.
Every particle has one.
When does annihilation take place.
When a particle and its antiparticle meet.
Describe the process of annihilation.
The mass of both is converted into energy in the form of 2 gamma ray photons which travel off in opposite directions, conserving momentum.
Describe Pair Production.
When a gamma photon is converted into a particle-antiparticle pair.
How to find the minimum energy of a photon required for pair production of any two particles?
2 x (the rest energy of that particle) measured in MeV
What do Kaons decay into?
Pions
Strange particles are produced by..?
The strong interaction and decay by the weak interaction.
What do muons decay into?
An electron and two types of neutrino
Which particles does the strong force affect?
Hadrons (not leptons)
What is Electromagnetic Repulsion?
You need to know the diagram for this.
When two particles with equal charges get close to each other and repel. Enacted by the virtual photon.
