Radiation Physics Equipment QA & Protection Ppt Flashcards
What are isotopes?
Same number of protons, different number of neutrons
What are isotones?
Isotones are atoms having nuclei with the same number of neutrons but a different number of protons.
What are isobars?
Isobars are atoms having the same atomic mass but a different number of protons.
What are isomers?
Isomers are atoms having the same number of protons and neutrons but at a different energy state.
What is the SI unit for absorbed dose?
The Gray (Gy) is the SI unit for absorbed dose.
What is a Gray equivalent to?
1 Gy = J/kg
What is the formula for wavelength, speed, and frequency of an electromagnetic wave?
c= frequency times wavelength
Speed of light (c)= lambda x frequency (f)
c= 3x10^8m/s
What is the beam direction of x-rays at low electron energies?
Almost right angles to the initial electron beam’s direction.
How does the beam direction of x-rays change at high electron energies?
At high energies, the x-rays emitted are in a more forward direction with less angular spread. As energy increases, the beam becomes more narrow and more intense in the forward direction.
What is the thickness of an absorber required to attenuate the intensity of a photon beam to half its original value?
The thickness is known as the half-value-layer (HVL).
What characteristic of the beam is the half-value-layer (HVL) related to?
The quality of an X-ray beam.
What is the linear attenuation coefficient (u)?
It is an expression of the probability of the photon being removed by a given material.
How is the linear attenuation coefficient related to the half-value-layer?
The relationship is given by the expression: u = 0.693 / HVL.
What does the linear attenuation coefficient depend upon?
It depends upon the density of the material.
How is the mass attenuation coefficient defined?
Mass attenuation coefficient = u / p.
What are the interactions of radiation with matter?
There are five major physical processes responsible for photon-beam attenuation:
1. Coherent scattering
2. Photoelectric effect
3. Compton effect
4. Pair production
5. Photo disintegration
