ABR 1 – Physics Questions And Answers
With Complete Solutions
US attenuation rule of thumb correct answer: 0.5 dB/cm*MHz in soft tissue
Lens dose is calculated at what depth? correct answer: 0.3 cm
How many HVLs in a collimator head? correct answer: 2% transmission, so 0.02=2^(-n)-> n=5.6, 6 HVL
Temperature and pressure correction correct answer: P0T/T0P, T0=295.2K
To maintain an accuracy of 1/x, how many bits are necessary? correct answer: 2^y=x, y=lnx/ln2
ex: 1 ppm -> 2^y=10^6-> 6ln(10)/ln(2)=19.93->20 bits
Given an air Kema = D mGy, what is the corresponding exposure? correct answer: D mGy = D*10^-3 Gy->D*10^-3/(33.8 J/C)/(2.58*10^-4 C/Kg*R)
Identify intensity vs distance graphs for a point source, line source, and plane source correct answer: point source will be ~1/r^2, line source ~thetaf*thetai/h, plane source of radius r will be ~ ln(r^2+h^2/h^2) on CAX
physical and biological half-life correct answer: N(t)=N_0*exp{-{0.693/Tr+0.693/Tb}} For beta decay, what is the average energy of the beta particle? correct answer: 1/3 E Max
For a radioactive isotope with a half-life of T 1/2 and an initial activity of A, how many disintegrations occur between T 1/2 and 2T 1/2? correct answer: A=lambda*N
N0 = A0/lambda-> A0/2lambda-A0/4lambda=A0/4lambda
HVL and TVL equations correct answer: Transmitted intensity = 10^(-x/TVL)=2^(-x/HVL)
Ion chamber: 1 cGy per 0.25 nC. What is the size of the ion chamber? correct answer: (0.25 nC/cGy/1.3 kg/m^3)->(0.25/1.3
nC*m^3/J)*(W/e)-> 0.25*33.97*10^-9/1.3 m^3
Given a magnetic field of strength x T, find the energy needed to
take a proton from parallel to anti-parallel correct answer: B=x T
h_bar = 6.626*1-^-34/2pi J*s*radian
phi = 2.68*10^8 radiation/T*s for protons
E = B*phi*h_bar
A source with activity of x Bq has a half-life of y days. What is the initial amount of atoms? correct answer: A = x = N0*lambda
lambda = 0.693/y
N0=xy*(24 hrs/day)*(60 min/hr)*(60 s/min)/0.693
Equations for total kerma, air kerma, and collisional kerma correct answer: K=phi(mu_tr/rho)
With Complete Solutions
US attenuation rule of thumb correct answer: 0.5 dB/cm*MHz in soft tissue
Lens dose is calculated at what depth? correct answer: 0.3 cm
How many HVLs in a collimator head? correct answer: 2% transmission, so 0.02=2^(-n)-> n=5.6, 6 HVL
Temperature and pressure correction correct answer: P0T/T0P, T0=295.2K
To maintain an accuracy of 1/x, how many bits are necessary? correct answer: 2^y=x, y=lnx/ln2
ex: 1 ppm -> 2^y=10^6-> 6ln(10)/ln(2)=19.93->20 bits
Given an air Kema = D mGy, what is the corresponding exposure? correct answer: D mGy = D*10^-3 Gy->D*10^-3/(33.8 J/C)/(2.58*10^-4 C/Kg*R)
Identify intensity vs distance graphs for a point source, line source, and plane source correct answer: point source will be ~1/r^2, line source ~thetaf*thetai/h, plane source of radius r will be ~ ln(r^2+h^2/h^2) on CAX
physical and biological half-life correct answer: N(t)=N_0*exp{-{0.693/Tr+0.693/Tb}} For beta decay, what is the average energy of the beta particle? correct answer: 1/3 E Max
For a radioactive isotope with a half-life of T 1/2 and an initial activity of A, how many disintegrations occur between T 1/2 and 2T 1/2? correct answer: A=lambda*N
N0 = A0/lambda-> A0/2lambda-A0/4lambda=A0/4lambda
HVL and TVL equations correct answer: Transmitted intensity = 10^(-x/TVL)=2^(-x/HVL)
Ion chamber: 1 cGy per 0.25 nC. What is the size of the ion chamber? correct answer: (0.25 nC/cGy/1.3 kg/m^3)->(0.25/1.3
nC*m^3/J)*(W/e)-> 0.25*33.97*10^-9/1.3 m^3
Given a magnetic field of strength x T, find the energy needed to
take a proton from parallel to anti-parallel correct answer: B=x T
h_bar = 6.626*1-^-34/2pi J*s*radian
phi = 2.68*10^8 radiation/T*s for protons
E = B*phi*h_bar
A source with activity of x Bq has a half-life of y days. What is the initial amount of atoms? correct answer: A = x = N0*lambda
lambda = 0.693/y
N0=xy*(24 hrs/day)*(60 min/hr)*(60 s/min)/0.693
Equations for total kerma, air kerma, and collisional kerma correct answer: K=phi(mu_tr/rho)
