Nuclear Physics Flashcards
Nuclide
A particular species of nucleus that is specified by its proton and neutron number
Isotopes
Isotopes are VARIANTS of the same element with the same number of protons but a different number of neutrons in the nucleus.
Mass defect
The DIFFERENCE in mass between the MASS OF A NUCLEUS and the total mass of its CONSTITUENT NUCLEONS.
Nuclear binding energy
The energy required to completely SEPARATE the nucleons in a nucleus to infinity.
Binding energy per nucleon (BE CLEAR if it is per nucleon or not)
The energy per nucleon required to completely separate the nucleons to infinity
Conservation of mass-energy
For an isolated system, the total mass-energy of the system remains constant.
Nuclear fission
Nuclear fission is the splitting of a nucleus of high nucleon number and low binding energy per nucleon into 2 smaller nuclei of approximately the same mass with higher binding energy per nucleon with the release of energy and neutrons.
Nuclear fusion
Nuclear fusion is the combining of two nuclei of low nucleon number to produce a larger nucleus with a greater binding energy per nucleon with the release of energy.
Radioactivity
Radioactivity is the spontaneous and random disintegration of the unstable nucleus, emitting some or all of the following nuclear radiations: alpha particles, beta particles and gamma radiations.
Spontaneous decay
Decay that is not affected by external or environmental factors.
Random decay
The nucleus has a constant probability for decay per unit time, where the time of decay of a nucleus cannot be predicted.
Activity of the radioactive nuclide
Activity of the radioactive nuclide is the number of nuclear disintegrations per unit time of the nuclei.
Decay constant
The constant probability of decay per unit time of a nucleus.
Half-life*
The average time taken from the initial number of that particular radioactive nuclide to reduce to half of its initial value.
Background radiation
The radiation detected by a radiation counter when there is no radioactive source nearby.
It is an unavoidable radiation arising from natural resources.
Count rate
Rate at which emissions from a radioactive source are detected.
Observations of Rutherford’s experiment
1) Most of the alpha particles were deviated through small angles or undeflected
2) A small but significant percentage of the alpha particles deviated through large angles greater than 90 and up to 180
Inference of most of the alpha particles were deviated through small angles or undeflected
For the structure of the atom, the nucleus exists and the size of the nucleus is small compared to the atom
Inference of a small but significant percentage of the alpha particles deviated through large angles greater than 90 up to 180
For the structure of the atom, the nucleus is charged and the mass is concentrated in the nucleus.
What is the maximum binding energy per nucleon for all nuclei?
8.8MeV (Fe-56)
Radioactive decay of an unstable nucleus
The emission of alpha, beta, and/or gamma ray photons with the release of energy and the formation of a more stable nucleus.
Penetrating ability of alpha particles + Range in air + Ionising strength + Typical energy
Stopped by a piece of paper
~1 to 3cm
Strong
Characteristic emissions
Penetrating ability of beta particles + Range in air + Ionising strength + Typical energy
Stopped by a few mm of aluminium
~1m
Weak
Continuous spectrum
Penetrating ability of gamma particles + Range in air + Ionising strength + Typical energy
Stopped by about 10cm of lead
~1km
Very weak
Characteristic emissions
The general equation for radioactive decay
x = x0e^(-lambda)(t)
Remember to minus background radiation!
What are the direct and indirect effects of ionising radiation on living tissues and cells?
- Direct damage to DNA through breaks and mutations
- Indirect generation of free radicals which initiate harmful chemical reactions within cells and cause similar effects as direct action.
At low levels of exposure, cells have mechanisms that can repair the damage, but with prolonged exposure, severe damage can lead to creation of tumour cells or cell death.
