Chapter 1 - Matter and Radiation Flashcards
State the quark composition of a meson.
a quark and an antiquark.
Name two mesons
The pion and the kaon for example.
Name the quarks making up a proton
Two up quarks and a down quark.
What’s the baryon number of a down quark?
A third - all quarks have a baryon number of 1/3.
A baryon is made of two strange quarks and an up quark. Give the charge and strange number of this baryon.
Charge = zero ( two -1/3 and a 2/3) Strangeness = -2.
What’s the difference between a hadron and a lepton?
A hardon is made of quarks, a non-fundamental particle. Leptons are fundamental particles.
Hardons experience the strong nuclear force. Leptons don’t.
Give similarities and differences between a muon and an electron.
Same charge - minus one, same lepton number, 1. Both experience three forces, weak force, electromagnetic force and gravity.
Different mass or rest energy - muons are heavy electrons.
Name 2 Baryons.
Proton and neutron for example.
State the baryon number of the K minus meson.
Zero - it is not a baryon, but is a hadron.
What is the quark composition of the K minus meson?
An anti up, charge -2/3 and a strange, charge -1/3.
Remember that kaons have strangeness.
Describe the interaction responsible for the decay of a strange quark to an up quark.
The weak interaction ( a W- Boson is formed which is the exchange particle for this interaction). Strange quark has -1/3 charge and an up quark has 2/3 charge.
Other than energy and momentum, state two quantities that are conserved when a W minus particle is produced due to a strange quark decaying to an up quark and one quantity that is not.
Conserved : charge and lepton number.
Not conserved : strangeness ( this does not have to be in weak interactions, only in strong)
What is meant by nucleon number?
The number of protons and neutrons in a nucleus.
State the units for specific charge.
C Kg-1
How do you calculate the specific charge of a carbon nucleus with a mass number of 12 and an atomic number of 6?
Specific charge = charge / mass
Charge = 6 X 1.6 X 10-19
Mass = 12 X 1.67 X 10-27
Divide these two values. The answer is large!
What is meant by the term isotope?
An atom with the same proton number as another but a different mass number (number of neutrons)
Protons and neutrons can interact through three fundamental interactions. Name them and give the exchange particles responsible for 2 or these 3 interactions.
Gravity or gravitational force
Electromagnetic force - photon
Weak force - bosons ( W plus, minus or Z zero)
What is meant by electron capture?
A shell electron interacts with a proton in a nucleus and a neutron is formed OR an u quark changes to a d quark.
State the quark structure of an antineutron.
Anti u anti d anti d
Give one property of an antiparticle that is the same as a particle and one difference.
Same : mass
Different : charge and baryon/lepton number.
What is specific charge?
Ratio of charge to mass of the nucleus.
What is the specific charge of an atom?
Zero, as it has the same number of protons as electrons.
Describe the process of pair production.
A photon interacts with an electron/nucleus/atom
Energy of the photon is used to create a particle and anti particle
Momentum is conserved as photon interacts with the electron/nucleus/atom.
Describe what occurs to a nucleus as a result of alpha decay.
The nucleus emits 2 protons and 2 neutrons. The mass lost is 4 units and 2 units of charge.
Why is an alpha particle unaffected by the strong force once outside the nucleus?
The strong force only acts over very short distances, up to 3 femto metres. It has a very short range. Beyond this there is no interaction.
Which sub atomic particle has the largest specific charge?
The electron, same charge as a proton but a much smaller mass.
Describe the changes that occur to a nucleus during beta minus decay.
A neutron changes to a proton and a W- Boson is formed.
This decays into an electron and an electron antineutrino.
The nucleus does not change in mass number, but the atomic number increases by one.
What is the quark structure of the K + kaon, which has a strangeness of +1?
An anti strange quark and an up quark.
A K+ kaon with a strangeness of 1 can decay into a muon neutrino and an anti muon.
Other than charge, energy and momentum, show another quantity that is conserved and one quantity that is not conserved.
Lepton number zero on left hand side and 1 -1 = zero on right hand side.
Strangeness not conserved +1 on left hand side, zero on the right.
Must be decaying through the weak interaction.
A K+ particle can decay to form a positive pion and one other particle.
Suggest which particle this is based on the laws of conservation.
Charge must balance and so it must be a neutral particle.
Lepton number must be conserved and so it can’t be a lepton such as a neutrino.
It must be a neutral meson, e.g. A pion-zero.
Two nuclei, one with 7 protons and 14 nucleons and the other with 9 protons and 19 nucleons.
Which nucleus has the smallest specific charge?
The one with a nucleon number of 19 as this has a smaller proton to mass number ratio 9/19 as a fraction is less than 7/14.
Describe how the strong nuclear force between a neutron and a proton varies with the separation of the two particles.
Between 3fm and 0.5 fm, the particles attract each other through the strong interaction. Above 3fm there is no force between particles at all. Below 0.5fm the force becomes repulsive, increasingly so as the separation becomes smaller.
Other than the strong force, give another interaction between two protons in a nucleus and name the exchange particle responsible for this interaction.
Electromagnetic
(virtual) Photon
Name a constituent of an atom which, when removed leaves a different isotope of that atom.
The neutron
It is possible for a photon to be converted into an electron and a positron. What is this process called and why can’t a single particle be produced?
Pair production
Both particles must be produced so that charge and momentum are conserved.
If a photon has more energy than needed to create an electron and positron pair what happens to this excess energy?
This goes into the kinetic energy of the positron and electron.
What is likely to happen to a positron that has been created through pair production?
It will collide with an electron and the two particles will annihilate to form 2 photons.
There are two groups of hadrons. Name them.
Baryons and mesons
Give two properties that distinguish hadrons from leptons.
Hadrons are non- fundamental particles, made of quarks.
Leptons are fundamental particles.
Hadrons experience the strong interaction, leptons don’t.
Hadrons eventually decay to a proton.
State the charge in coulombs of a magnesium atom after losing 2 electrons.
The ion will have a 2+ charge and so has 2 more protons than electrons. Charge in coulombs = 2 X 1.6 x 10-19.
A magnesium ion with 12 protons and 24 nucleons loses 2 electrons. Calculate the specific on the ion formed.
Specific charge = charge / mass
Charge = 2x 1.6 X 10-19
Mass = 24 X 1.66 X 10-27 + 10 X 9.11 X 10-31
Specific charge = 8.03 X 10+6 C Kg-1
Give two differences between the exchange particles boson and a photon.
Boson W- or W+ are charged, photon is not.
Bosons have a rest mass, photons do not.
Photon has an infinite range, bosons do not.
