Flashcards in Nuclear Physics Deck (30)
What are the three types of radiation?
What must be measured first before a source's count rate is tested?
How do the radiation types deflect in a magnetic field?
Alpha and beta deflect in opposite directions
Beta deflects more than alpha due to its smaller mass
Gamma is not deflected
Define intensity of radiation
The radiation energy per second passing normally through unit area
Describe the alpha particle scattering experiment
Alpha particles were fired at very thin gold in a vacuum. A phosphorous screen around the outside showed where the alpha particles traveled
Describe the observations and conclusions from the alpha particle scattering experiment
Most of the fast, highly charged alpha particles went straight through undeflected - SUGGESTS THAT MOST OF THE ATOM IS EMPTY SPACE
Some of the alpha particles were deflected through large angles. - SUGGESTS THAT THERE IS A CONCENTRATED POSITIVE MASS SOMEWHERE IN THE ATOM.
A very small number of alpha particles were deflected backwards - SUGGESTS THAT THE CONCENTRATED MASS IS MINISCULE COMPARED TO THE SIZE OF THE REST OF THE ATOM, BUT CONTAINS MOST OF THE MASS
In a nuclear reaction what must be conserved?
Describe an alpha particle
2 protons and 2 neutrons or a helium nucleus
relative mass = 4
relative charge + 2
Stopped by skin, paper 10 cm air
Describe a beta particle
an electro emitted from the nucleus
relative mass = almost 0
relative charge -1
Stopped by mm's of aluminium or 1 meter of air
Describe a gamma wave
electromagnetic wave moving at the speed of light
relative mass = 0
relative charge 0
Very weakly ionising
Reduced by cm's lead or meters of concrete
What changes does alpha decay cause to the daughter nucleus?
Mass number decreases by 4
Proton number decreases by 2
What changes does beta decay cause to the daughter nucleus?
Mass number stays the same
Proton number increases by 1
What changes does gamma decay cause to the daughter nucleus?
Mass number stays the same
Proton number stays the same. the nucleus just losses some energy
What changes happen in beta decay?
A neutron decays into a proton creating a beta particle and an electron antineutrino.
A down quark decays into an up quark.
The rate at which any substance emits radioactive particles is called the activity. The activity is measured in Becquerels (Bq)
Define count rate
The count rate is simply the number of particles that are counted by a Geiger counter (or some kind of measuring device)
What factors will affect the activity of a substance?
The number of particles there are in the substance
The natural tendency of a substance to decay (i.e. some substances are naturally more likely to decay more than others)
Define half life
The half life of a substance is the time it takes for half the number of particles in the substance to decay. It can also be seen as the time it takes for the activity of a substance to fall to half its current value.
Define the atomic mass unit
It is equal to exactly 1/12th the mass of a carbon 12 atom
Define the electronvolt
The electronvolt (eV) is the energy gained when 1 electron accelerates through a p.d. of 1 volt
How can you convert from eV to J?
1 eV = 1.6 x 10-19 J
how can you convert from MeV to eV
1 x 106 eV = 1MeV
Define mass defect
The difference between the mass of an atom and the mass of its individual particles is known as the Mass defect, Δm.
Define binding energy
The binding energy of a nucleus is the energy that would be required to separate a nucleus into its separate constituents
Define binding energy per nucleon
average energy needed to "break off" just one nucleon from the nucleus.
What is the role of fuel rods in a nuclear reactor?
Contained in the reactor core and generally made of enriched uranium. Act as fuel source of the fission reactor
What is the role of the moderator in a nuclear reactor?
Usually made of carbon and also part of the reactor core. Slows down neutrons within the reactor core allowing them to fuse with the uranium and make fission reactions
What is the role of the control rods in a nuclear reactor?
Made of boron, which can absorb neutrons. These can be lowered into the reactor to control the rate of fission.
What is the role of the coolant in a nuclear reactor?
The coolant absorbs the heat from the fission reactions. It is then used to heat up water and turn it into high pressure steam