Nuclear Physics Flashcards
Define binding energy
Binding energy of a nucleus is defined as the energy needed to completely separate the nucleus into its constituent protons and neutrons to infinity.
What is mass defect?
Mass defect is defined as the difference between the mass of the nucleus and its constituent protons and neutrons.
Binding energy = mass defect x c^2
Charcteristics of binding energy per nucleon against nucleon number graph
Most nuclides have BE per nucleon between 7.5 to 9 MeV
Nuclides around Fe-56 have the highest BE per nucleon of about 8.8 MeV
What is a fission and fusion reaction?
A fission reaction is one in which a heavy nucleus splits into lighter nuclei to release energy.
A fusion reaction is one in which light nuclei combine to form a heavier nucleus to release energy.
What is radioactive decay?
Radioactive decay is a spontaneous and random process in which an unstable nucleus disintegrates to form a more stable nucleus, emitting alpha, beta and/or gamma radiation in the process.
Define activity
The activity A of a radioactive sample is defined as the number of decays per unit time in the sample.
The unit for activity is Bq (becquerel) where 1 Bq = 1 decay/s
Define decay constant
The decay constant λ of a radioactive sample is defined as the ratio of the number of decays per unit time in the sample to the number of radioactive nuclei.
Define half-life
The half life t1/2 of a quantity is defined as the time taken for the quantity to decrease to half of its initial value.
t1/2 = ln2/λ
What does the scattering pattern prove?
The nuclear model of the atom provides the conditions to produce the scattering pattern of the alpha particles observed in the experiment. The small deflections are produced when the alpha particle pass close to the nucleus. The large deflections are produced when the alpha particles approach the nucleus head-on
Define random
It cannot be predicted which nuclide will decay at a particular instant or when any particular nuclide will decay.
Define spontaneous
It is not triggered by external factors such as temperature and pressure.
Proof of neutrino
By the principles of conservation of energy and of momentum, radiation particles should be emitted with a predictable amount of energy and predictable momentum.
Beta particles emitted from the same source have varying kinetic energies.
Also, the daughter nuclei of beta decay do not recoil in the opposite direction of the emitted beta particles, but in varying directions.
Hence, by the principles of COE and COM, there must be another particle to account for the discrepancies in energy and momentum, which is the neutrino.
