Chapter 1: Particles And Radiation Flashcards
Describe the structure of an atom.
There is a nucleus comprised of neutrons and protons which electrons orbit. Most of an atom is empty space.
What is the relative charge of each particle in the atom.
Proton = 1+
Electron = 1-
Neutron = 0
Give the relative masses of each of the particles in the atom.
Proton = 1
Electron = 1/2000
Neutron = 1
What is the proton number of an atom?
The number of protons in the nucleus. Represented by the letter Z.
What is the nucleon number of an atom?
The total number of protons and neutrons in an atom. Represented by the letter A.
What is specific mass and what units is it measured in?
The charge of a particle divided by its mass. It is measured in C kg^-1
What are isotopes?
Atoms with the same number of protons but a different number of neutrons.
Give an example of how isotopic data can be used.
To calculate the age of organic matter. This is done by calculating the percentage of carbon which is radioactive carbon-14 present in the object being studied.
What are the two largest forces acting on the particles in a nucleus?
The electromagnetic force (between protons) and the strong nuclear force.
What is the range of repulsion of the strong nuclear force?
Between 0 and 0.5 fm.
What is the range of attraction of the strong nuclear force?
Between 0.5 and 3 fm.
Explain how we know there must be a strong nuclear force.
The electrostatic repulsion is much greater than the gravitational attraction. Without another force, the strong nuclear force, the nucleus would fly apart.
What is a ß- particle also known as?
A electron
Why does a nucleus undergo nuclear decay?
Because the forces in the nucleus only have a range of a few femtometres, so they struggle to hold larger nuclei together. This makes the nucleus unstable.
How do the nucleon and proton numbers of an atom change in alpha decay?
Nucleon number decreases by 4.
Proton number decreases by 2.
Give two ways of demonstrating the range of alpha particles.
- Using a cloud chamber to observe tracks left by alpha particles.
- Using a Geiger counter or spark counter to measure the amount of ionising radiation at different distances from an alpha source.
What particles are emitted during beta-minus decay?
An electron and an antineutrino.
What type of nuclei will decay by beta-minus decay?
Neutron rich nuclei.
Describe the changes in the nucleus of an atom when it undergoes beta-minus decay.
A neutron turns into a proton, so the nucleon number stays the same and the proton number increases by 1.
Explain how the neutrino was hypothesised as a result of beta decay.
It originally appeared as though energy was being lost in beta decay. A new particle was hypothesised in order for energy to remain conserved. This particle had to be neutral and was named the ‘neutrino’.
What is a photon?
A ‘packet’ of EM radiation.
What equation would you use to calculate the energy of a photon from its wavelength?
E = hc/λ
How is an antiparticle different and the same from its corresponding particle?
It has the opposite charge but the same mass and rest energy.
What is the relative charge of the antineutrino?
0
Describe the process of pair production.
Energy can be converted into mass and produce particles, if there is enough energy. The mass is always produced in a particle-antiparticle pair.
What is produced in the annihilation of matter and antimatter?
Two gamma ray photons.
What type of particle feels the strong nuclear force?
Hadrons
What particles is believed to be the only stable baryon?
Proton
Write down the baryon number of:
1. Electron
2. Antineutron
3. Kaon
- 0
- -1
- 0
What particles are produced when a neutron decays into a proton?
An electron and antineutrino (and a proton).
Explain what cosmic ray showers are.
High-energy particles produced as a result of radiation from space interacting with molecules in the atmosphere.
What is the relative charge of an antimuon?
+1
In what type of interaction are strange particles produced in pairs?
Strong interaction
What special property do strange particles have?
Strange particles are always produced in pairs.
In what type of interaction do strange particles decay?
The weak interaction
In which interaction is strangeness not conserved?
By how much can strangeness change in this type of interaction?
The weak interaction. Strangeness can be changed by -1, 0 or +1.
What properties are always conserved in particle interactions?
Charge, baryon number, lepton number, mass, energy, momentum.
Name 3 quarks.
Up, down and strange
What is the baryon number of a quark?
-1
What is the quark composition of a meson?
1 quark and 1 antiquark
Why can you not have a quark on its own?
The energy used to remove a quark from a hadron creates a quark-antiquark pair. It’s called quark confinement.
What sort of interaction can change a quark’s character? Name and describe an interaction in which this happens.
The weak interaction. In ß- decay, a neutron decays to a proton so a down quark changes to an up quark.
What is an exchange particle?
A virtual particle that lets a force act between two particles in an interaction.
Name the electromagnetic force exchange particle.
Virtual photon
Name two exchange particles of the weak interaction.
W+ and W- bosons
What do the straight lines on particle interaction diagrams represent?
Particles
Why would a nucleus undergo electron capture?
Because it is proton rich.
What is the difference between electron capture and electron-proton collisions?
In electron capture, a proton in a nucleus captures an electron from the atom, turning into a neutron and emitting a neutrino. In an electron-proton collision, a free electron collides with a free proton, producing a neutron and a neutrino.
What are the exchange particle for electron capture, and what particles are produced?
The W+ boson is the exchange particle and a neutron and an electron neutron are produced.
