Nuclear Physics Flashcards
(26 cards)
What’s the size of a nucleus
Nucleus diameter is 10*-15
Nucleus is 1/10000 of an atom
Describe alpha particle scattering experiment
Alpha particles fired at thin Gold foil by alpha source.
Takes place in an evacuating chamber, covered in fluorescent coating
Path of the alpha particles observed through a microscope
What was deduced by the results of the alpha particle scattering experiment
.disproved plum pudding model since if it was true, the alpha particles would only be deflected by a small amount
Most Alpha particles passed straight through the foil with no deflection= atom mostly empty space
Some deflected by large angle= centre positive charge
Very few particles deflected by >than 90degree = very dense centre
Radiation properties
Alpha - 2-10cm range, high ionisation, effected by both fields, stopped by paper
Beta - 1 cm range in air, weak ionisation, effected by both fields, stopped by Aluminium foil
Gamma - infinite range but decrease in intensity 1/x^2 , several meters of concrete or few inches of Lead to stop
Actions you can take to handle radioactive sources
Handle with long handed tongs,
Store the source in a lead lined container
Source far away, dont point source at others
Background radiation
From radon gas produced by rocks, cosmic rays, nuclear weapon tests + meltdowns, radioactive rocks
What is the decay constant
Probability of a nucleus decaying per unit time.
-λN
Decay over long time= N=n0e^-λT
Half life?
Time taken for the amount of radioactive nuclei in a sample to halve
Half life = Ln2/ λ
A=a0e^- λT
Nuclear instability
The strong force holds the nucleus together but when the protons and neutrons out of balance, so are the electrostatic forces, making the atom unstable
A particle may also decay since it has too much energy, in the form of gamma radiation
Finding the nuclear radius( closest approach)
The distance of closest approach of a particle, can help estimate the nuclear radius of an atom
When a charged particle getting closer and closer to the atom stops and has no KE, that’s the distance of closest approach
But this value from this method is always an overestimate
Re arrange the following equation -
Electric energy=1/4πE0 x Q1Q2/r^2
what is the variation of Einstein’s equation for annihilation of particles
its E= 2MC^2
Electron diffraction method for the radius of a nucleus
This method more accurate estimate since electrons are leptons - therefore don’t interact with nucleus + it’s strong force
define binding energy
energy required to completely separate a nucleus into its constituent atoms
define mass defect
differrence between the mass of a completely separated nucleus and the nucleus itself
define binding energy per nucleon
min energy required to remove a nucleon from the nucleus
fusion and fission
fusion = 2 light nuclei combining to make a heavier nuclei
Fission = 1 heavy nucleus into 2 light nuclei
irons stability -
iron56 is the most stable nucleus,
elements with a greater formula mass than iron have Less binding energy per nucleon, therefore no fusion
elements with a lower formula mass than iron cannot do fission since the binding energy per nucleon will decrease
bigger binding energy means
more energy released
parts of a nuclear reactor
Fuel rods - contain uranium fuel
Control rods - absorb some of the neutrons to control the rate of the nuclear reaction
moderator - slows down the fast moving neutrons to create thermal neutrons ( an example of a moderator is water )
Nuclear fusion conditions
High temp + pressure to overcome the electrostatic repulsion
higher probability of nuclear fusion the higher the temp + pressure
nuclear reactor process
- fission to release energy
- control rods manage rate of fission
- Moderators improve likelihood of further fission
4.coolant carries the heat away from the reactor core, transferring the heat onto water to be turned into steam, which can turn a turbine
Nuclear energy -> thermal energy -> Mechanical energy
inside a nuclear reactor
Reactor core, with control rods in, the fuel rods in and containing moderator and coolant. The site of where the fission takes place.
this core containing those things, is connected to a system to pump in and out coolant to then bring steam to turbines
this is ALL incased in a concrete shield to make sure no gamma radiation escapes or neutrons, and also maintains the temp of the reactor, and helps incase any malfunctions in the reactors
for N - Z graphs what also is there to consider
when showing the decay of a particle by beta plus/ beta minus, take into consideration that the neutron number decreases in the case of beta plus decay
why may some nucleotides undergo fission whilst other nuclei undergo fusion
. Energy is released if the binding energy per nucleon increases
. In fusion, 2 smaller nuclei fuse to form a bigger one,
. In fission 1 larger Nucleus breaks down into a smaller one
. the most stable nuclei are at a peak on the graph, towards its left undergoes fission, to its right it undergoes fusion
