Nuclear Physics and Particles Flashcards
How do you calculate the mass defect of a nucleus?
The mass defect of a nucleus is defined as the difference between the mass of the separated nucleons and the combined mass of the nucleus.
What is nuclear fusion?
is the combining of the two light nuclei to produce a heavier nucleus.
What is nuclear fission?
is the disintegration of a heavy nucleus into two lighter nuclei of approximately equal masses.
Define radioactive decay
is the spontaneous decaying of the nucleus of an atom which results in the emission of particles.
What is background radiation?
Ionizing radiation emitted from a variety of natural and artificial radiation sources. It should be constant isotropic and uniform
What is the activity of a sample?
The activity of a radioactive substance is defined as the average number of atoms decaying per unit time.
What is the decay constant?
The decay constant λ of a nucleus is defined as its probability of decay per unit time
Define half-life
Half-life is defined as the time taken for half the original number of radioactive nuclei to decay
Explain the role of the moderator
The moderator slows down fast neutrons making them thermal neutrons to make fission more likely to happen.
What are possible materials for the moderator?
Water, Graphite.
What is the role of the control rods?
Reduce the number of neutron in the fission reactor
What are possible material for control rods?
Boron and Cadmium
Define the Nuclear Binding Energy
Nuclear binding energy is the energy required to disassemble a nucleus into the free, unbound neutrons and protons it is composed of
proton number
number of protons in the nucleus of an atom (a.k.a. atomic number)
nucleon number
number of neutrons and protons in the nucleus of an atom (a.k.a. mass number)
What are Isotopes
Different forms of the same element or nuclei having the same number of protons with different
numbers of neutrons
Which group of particles are subject to the weak nuclear force but not the strong nuclear force
Leptons
What is the quark composition of a meson?
A quark and an antiquark.
Which force do Hadrons decay by?
The weak nuclear force.
What is the quark composition of a Baryon
Three quarks
What is a neutrino?
A lepton with no charge and a tiny mass.
Why doesn’t a neutrino experience the electromagnetic force?
They have no charge.
What is the quark composition of a neutron?
up down down (udd)
What is the quark composition of a proton?
up up down (uud)
What is the quark composition of an anti-baryon?
Three antiquarks
Name the two types of hadron.
baryons and mesons
What force hold quarks together in hadrons?
The strong nuclear force.
What is the family of particles that are subject to both the strong and weak nuclear force?
Hadrons
What type of particle are nucleons?
Baryons
How does a proton compare to an antiproton?
he have the same mass but opposite charge.
How does an electron compare to a positron?
The have the same mass but opposite charge.
What is the antiparticle of the electron?
Positron.
Describe beta minus decay.
A neutron in an unstable nucleus decays into a proton, electron and electron antineutrino.
Describe beta plus decay.
A proton in an unstable nucleus decays into a neutron, positron and an electron neutrino.
What quark transformation occurs during beta minus decay?
A down quark (in a neutron) turns into an up quark (in a proton)
What quark transformation occurs during beta plus decay
An up quark (in a proton) turns into an down quark (in a neutron)
What is the maximum range of the strong nuclear force?
~3fm
Below what distance is the strong nuclear force repulsive?
0.5fm
How did Rutherford estimate the maximum radius of the nucleus?
He equated the KE of the alpha particle to the electric potential energy at closest approach to the nucleus.
What material was used as a target in Rutherford’s scattering experiment?
Gold foil, a few atoms thick
What was measured in Rutherford’s scattering experiment?
The angle of deflection of the alpha particles.
What happened to most of the alpha particles in Rutherford’s scattering experiment?
They passed straight through the foil (with very little scattering).
What proportion of alpha particles were scattered in Rutherford’s scattering experiment?
Around 1 in 2000
What proportion of alpha particles were deflected by more than 90° in Rutherford’s scattering experiment?
Around 1 in 10,000
What was concluded due to most of the alpha particles passing straight through the gold foil Rutherford’s scattering experiment?
Most of the atom is empty space with most of the mass concentrated in a small nucleus.
What was concluded due to some alpha particles being scattered in Rutherford’s scattering experiment?
The nucleus is positively charged.
How did Rutherford estimate the maximum radius of the nucleus?
He equated the KE of the alpha particle to the electric potential energy at closest approach to the nucleus.
How has the radius of the nucleus been measured?
By the diffraction of fast moving electron.
What is R in R = r₀A^(1/3)?
The radius of the nucleus.
What is r₀ in R = r₀A^(1/3) roughly equivalent to?
The radius of a proton.
What is A in R = r₀A^(1/3)
Nucleon number.
What is the activity of a sample?
The activity of a radioactive substance is defined as the average number of atoms disintegrating per unit time.
