Nuclear And Particle Physics Flashcards
Rutherford’s observations and conclusions
- The atom is mainly empty space as when alpha particles were shot at gold foil they pass through undisturbed
- The nucleus has a large positive charge charge as alpha particle were deflected less than 90 degrees
- The nucleus is small as some alpha particles were deflected at angles greater than 90 degrees
Strong nuclear force
- A force that acts between all nucleons with a very short range
- The force is repulsive below 0.5fm
- The force is attractive to about 3fm
Mean density of atoms
10³ kgm⁻³
Mean density of nuclei
10¹⁷ kgm⁻³
Hadrons
A particle or antiparticle affected by the strong nuclear force and weak nuclear force (causes decay). Eg protons and neutrons
Lepton
Particle and antiparticles that are not affected by the strong nuclear force but affected by the weak nuclear force e.g. Electrons and neutrinos
Quark model for a proton
uud
Quark model for a neutron
udd
Beta-minus decays
¹₀n ——> ¹₁p + ⁰₋₁e +
d ——> u + ⁰₋₁e +
= antineutrino
Beta plus decay
¹₁p ——> ¹₀n + ⁰₊₁e + v
d ——> u + ⁰₊₁e + v
⁰₊₁e= positron
v= neutrino
How is decay described
Random:
- cannot be predicted when a particular nucleus will decay
- each nucleus has the same chance of decaying
Spontaneous:
-Not affected by other nuclei or external factors
Half life
Average time for half the number of active nuclei in the sample to decay
Radioactive dating/ carbon dating
In carbon dating the ratios of carbon 14 to carbon 12, is compared in dead matter to similar living matter.
Rations of radioactive material is used for dating
Binding energy
Minimum energy required to completely separate a nucleus into protons and neutrons
Mass defect
The difference between the mass of the completely separated nucleus and the mass of the nucleus
Binding energy per nucleon
The greater the binding energy per nucleon the more tightly bound the nucleus/ more stable it is
Fuel rods
Contain enriched uranium mainly uranium 238
Moderator
- It slows down fast moving neutrons so that they can be absorbed by fuel rods. Eg water is a moderator
- The moderator also acts as a coolant which removes heat from the fuel rods
Control rods
- Rods made of material that absorbs neutrons
- They are moved so that only one neutrons survives per fission to be absorbed by the next fuel rod
Environmental impact of fission
The used fuel rods are toxic and have a long half life so they have to be buried deep underground. It must not enter food or water supplies
Measuring half life (dice method)
- Using die roll them and every time they land on a certain face e.g. Even you remove them
- Record the number of die each turn until there are no more die
- Then plot the number of die left to the number of turns taken
Measuring half life
- Using a geiger muller tube find the background count rate
- In a seal bottle mix protactinium-234 with uranium salt and shake
- Record the counts for 10s for every 30s
- Plot count rate against time
