Lecture 4 and 5. Radiation Physics Flashcards
What 2 things make up the nucleus of an atom?
Protons and Neutrons
What are isotopes?
Atoms of an element that have the same number of PROTONS
Nuclide nomenclature
What is the force that holds the nucleus of an atom together?
Nuclear force
What is a radioisotope?
An isotope of an element that is unstable and undergoes radioactive decay (eg. Carbon-14)
T or F. We can have radiation without radioactivity
True
NB: Examples are sunlight, microwaves, radiowaves
What is ionization?
The removal of electrons from an atom
What is radioactivity?
The property of an unstable atomic nucleus such that it disintegrates to a new state by releasing energy as photons, particles, or both
The modes of radioactive decay
Which type of radioactive decay produces a helium nucleus?
Alpha decay
T or F. Beta negative particles behave the same as electrons
True
Which process involves the transformation of a neutron into a proton?
Beta negative decay
Which process involves the transformation of a proton into a neutron?
Beta positive decay
What is another name for isomeric transition?
Gamma emission
What is Alpha decay?
When an unstable nucleus emits an alpha particle (2 protons, 2 neutrons), reducing its atomic number and mass.
What is beta negative decay?
When a neutron converts into a proton, emitting an electron and an antineutrino, increasing the atomic number.
What is beta positive decay?
When a proton converts into a neutron, emitting a positron and a neutrino, decreasing the atomic number.
What is electron capture?
When an atom’s nucleus absorbs an inner electron, converting a proton into a neutron and emitting a neutrino.
What is isomeric transition?
When a nucleus in an excited state releases excess energy as gamma radiation without changing proton or neutron numbers.
What is spontaneous fission?
When a heavy nucleus splits into smaller nuclei, releasing neutrons and energy without external influence.
What is the Becquerel?
One radioactive transformation per second
NB: It is the SI uni of radioactivity
What is the traditional unit of radioactivity?
The Curie (Ci)
What is half-life?
The time to decay to one-half of the initial value
What is a decay chain?
A series of radioactive decays where unstable nuclei transform until reaching a stable state.
What are primordial radionuclides?
Each of the isotopes is the head of a separate decay chain
What is radiation?
This is energy that is transmitted without the need for a physical medium
What is Period?
The time required to complete one cycle of a wave
What is frequency?
The number of periods that occur per second
What is non-ionizing radiation?
This is radiation that does not have enough energy to remove electrons from surrounding atoms
What is ionizing radiation?
Radiation that has enough energy to dislodge electrons (create “ions”)
What is the threshold energy for ionization in water?
13 eV
What is direct ionization?
When charged particles produce dense ionization through direct EM interaction with orbital electrons
What is indirect ionization?
When uncharged particles liberate one orbital electron which then produces relatively dense ionization along its path
What is charged particulate radiation?
This is when atomic or subatomic particles (electrons, protons, etc) carry energy in the form of kinetic energy of mass in motion
What is electromagnetic radiation?
When energy is carried by oscillating electrical and magnetic fields travelling through space at the speed of light
What is the range (or CSDA range)?
The depth in a medium at which all the charged particles completely stop
T or F. Alpha particles have a short range
True
Alphas or Betas, which one has stronger penetrating power?
Betas
What is Bremsstrahlung radiation?
When a projectile electron slows down as it comes close to the nucleus. It loses kinetic energy which is converted to an x-ray
NB: Brem is negligible for all particles except ELECTRONS
T or F. Plastic (low Z) material is better for shielding beta radiation compared to metal (high Z)
True
Describe the path length and range of Alpha and Beta particles
Alpha path length: straight (range)
Beta path length: segmented (path length is sum of segments)
What is the photoelectric effect?
When an atom absorbs a photon, it releases the excess energy by ejecting an orbital electron
What is the predominant interaction of incident photon of low energy with high Z materials?
Photoelectric effect
What is Compton scattering?
Inelastic scattering of a photon by a charged particle, usually an electron resulting in decrease in energy of the incident photon
What is pair production?
When a photon interacts strongly with the EM field of an atomic nucleus, giving up all its energy, creating a pair consisting of a positron and an electron
What is the minimum photon energy required to create a pair of electrons in pair production?
1.022 MeV
What is half-value layer (HVL)?
The thickness of an absorber that decreases transmitted beam intensity by one-half
Rank the types of radiation from most penetrating to least penetrating
- Neutron
- Gamma and X-rays
- Beta radiation
- Alpha radiation
Graph of photon interactions
