Chapter 2: Interactions of Radiation with Matter Flashcards
Sigma is the ____________ which describes the probability of interaction in a certain area.
interaction cross section
Lambert-Beer law describes ____________ in _________.
radiation attenuation/absorption
homogenous solutions
The molar extinction coefficient for strong absorbers is around _________.
10^4 M-1 cm-1
The two attenuation coefficients for radiation dosimetry are _________ and __________.
energy transfer coefficient
energy absorption coefficient
Etr is _____________.
Eab is _____________.
Typically Eab ____ Etr.
average energy transferred to charged particles in the matter
average energy absorbed by the charged particles in the matter.
<=
Attenuation can occur due to a number of processes such as _________ or _________.
absorption
scattering
The probability/cross section for each interaction depends on ____________ and __________.
energy of the photon, given by hv
atomic number of attenuator
The four types of photon interaction are ____________, ____________, ____________, and _____________.
coherent/elastic scattering
non-ionizing interaction
ionizing interactions
photonuclear effects
________________ has no biological radiation effects and makes up less than a couple % of the total attenuation coefficient.
____________ is also minor.
coherent/elastic scattering
photonuclear effects
____________ is a type of non-ionizing interaction.
__________, _____________, __________ are types of ionizing interactions.
Excitation
Photoelectric effect, Compton scattering effect, Pair production
The three types of transitions for absorption of energy by a molecule are __________, __________ and __________.
electronic, vibrational and rotational
Electronic transitions have energy ________ and result in ___________.
Vibrational transitions have energy ________ and result in ___________.
Rotational transitions have energy ________ and result in ___________.
1.7-10.8 eV
visual/ultraviolet light waves
0.04-0.4 eV
infrared light waves
0-0.04 eV
microwaves
1 eV = _________ J
1 cal = _______ J
1.6 x 10^-19
4.18
For ionizing interactions, the process by which x-ray photons are absorbed depends on __________ and __________.
energy of photons
chemical composition of absorbing material
Ionizing photon interactions have _______ transmission through thick material, are ________ ionizing and for higher energy have __________ penetration.
good
indirectly
higher
__________ is when a photon ejects an electron from an atom and all the photons energy is absorbed by the atom to remove the electron from its shell. The photon _________.
photoelectric effect
ceases to exist
A ________ is a particle of EM radiation with no mass, no electric charge and carries a quantum of energy hv.
photon
An _________ is when, during the photoelectric effect, when an e- drops down to fill the vacant shell, the energy released causes an outer shell e- to be ejected.
auger electron
The interaction cross section for the photoelectric effect is given by _________. It is strongly dependent on Z, and n = _____ for high Z elements, and n = _____ for low Z elements.
sigma = Z^n / (hv)^3
3
4
__________ is when a photon ejects an electron from its shell but not all of its energy is absorbed by the electron, causing a new photon with _______ wavelength and _______ energy. The new photon can cause __________. This interaction is also a _________ event.
Compton effect
shorter
less
further ionization
single electron
The probability for compton scattering depends on __________ and is proportional to ___________ and linearly proportional to ___________.
number of electrons in the medium
Z/atomic number
cross section sigma
________ is when the photon moves towards the nucleus and changes into electron-positron pair. The positron immediately joins with an electron, annihilating the positron and emitting two new photons with equal but half the energy of the original photons.
Pair production
The photoelectric effect dominates at ________ energies (_______), pair production dominates at ________ energies (_______), and compton effect dominates at _______ energies (________).
low
0.01-0.07 MeV
high
20-100 MeV
medium
0.1 - 10 MeV
The gap between attenuation and absorption for mass absorption is due to ___________.
loss of photon from Compton
Photon radiation is ________ ionizing because ____________.
indirectly
electrons ionize much more efficiently
Neutrons interact with ________ of the atoms, resulting in ________ or _________ or hit an oxygen atom to produce _________.
recoil photons
spallation products
four alpha particles
Ions interact with matter through 3 different processes depending on their energy:
1. ____________, _____ energy
2. ____________, ______ energy
3. ____________, ______ energy
These are ______ ionization interactions.
electron capture, low
collisions with atomic electrons, medium and high
nuclear collisions and nuclear reactions, very high
direct
The four processes in which electrons interact with matter are _________, __________, ___________ and ___________.
collisions with shell electrons
bremsstrahlung
cherenkov radiation
nuclear reactions
_________ is emitted when a charged particle passes through a dielectric medium at a speed greater than the phase velocity of light in that medium. The charged particles polarize the molecules of the medium, which then rapidly turn back to their ground state, emitting radiation in the process.
Cherenkov radiation
The speed of the propagation of light in water is ________.
0.75c
For cherenkov radiation if the particle travels slowly, then ______________ as particle passes. If the particle is moving very fast , then ________________ as particle passes.
disturbance relaxes elastically back to mechanical equilibrium
a disturbance is left behind and the energy contained in this radiates
Cherenkov radiation has biomedical applications in ______________, _____________, and ______________.
detection of labelled biomolecules
medical imaging of radioisotopes
external beam radiotherapy
Cherenkov radiation is emitted by ___________ for detection of labelled biomolecules.
phosphorus-32
For indirectly ionizing radiation, most of the primarily absorbed energy goes to _________ which _________.
secondary particles
cause ionizations and excitations in the matter
In photon radiation __________ are secondary particles.
electrons
