Base physics Flashcards
Coulomb interaction
F=kq1q2/r2
Kinetic energy
KE = mc2 – mc02
Force on a charged particle in magnetic field
F = qvB r = mv/qB
Exponential decay of a radioactive isotope
N = N0e-λt λ = 0.693/T1/2 N = N0 x 2-t/T1/2 Tavg = 1.44 T1/2
Activity
A = N0 λ e-0.693/T1/2 = A0 e-0.693/T1/2 = A0/2t/T1/2
Transient equilibrium
Ad=Ap*Tp/(Tp-Td)
Secular equilibrium
Ad=Ap
Photo electric effect
Eelectron=hv-Ebind
P~(Z/E)^3
Compton electron
Eelectron=hv-hv’=hv*a(1-cosx)/(1+a(1-cosx))
Compton photon
hv’=hv/(1+a(1-cosx))
probability of compton
1/e
~electrondencity
~dencity
Compton Scattered photon at 90deg
energy = 0.511 MeV
Compton Scattered photon at 180deg
Energy = 255
Pair production energy threshold
Energy threshold > 1.022 MeV
Pairproduction probability
~Z^2
~ln(E)
KERMA
non-stochastic quantity applied to indirectly ionizing radiations = kinetic energy released in matter (per unit mass)
CEMA
non-stochastic quantity applicable to directly ionizing radiation (electrons, protons) = converted energy per unit mass
TERMA
total energy released in matter
Initial dose build-up
Caused by kerma that generates secondary
electrons and releases energy in the medium
equivalent square
eq=2ab/(a+b)
Tissue-Air Ratio
TAR=Dd/Dfs
Back scatter factor
TAR at dmax
Scatter-Air Ratio
Used to calculate scattered dose in the medium
SAR=TAR(d,r)-TAR(d,0)
Resistance
R=v/I
Capacitance
C=q/V
inductance
V_L=Ldi/dt
