Physics

Question 1

Wave properties of light

Answer 1

c = λv

i.e. shorter λ = higher v b/c c constant

c = 3 x 10^8, v = freq

Question 2

Particle characteristics of light

Answer 2

E (keV) = hv = hc / λ = 1.24 / λ (nm)

i.e. shorter λ = higher E

h = 6.626 x 10^-34 J s
= 4.136 x 10^-18 keV s

Question 3

Minimum threshold E for ionization

Answer 3

11 eV for H20 (= 113 nm, far UV)

varies by molecule

Question 4

Size of atom vs. nucleus

Answer 4

Atom = 10^-10 m
Nucleus = 10^-14 m (very high density!)

Question 5

Max number of electrons per shell

Answer 5

2n^2

where n = quantum number (corresponding to shell K, L, M, etc)

Question 6

Characteristic x-ray def & nomenclature

Answer 6

E_char = E_vacant - E_transition

Named after vacant orbital:
L -> K denoted K_α  (K series)
M -> K denoted K_β  (K series)
M -> L denoted L_α  (L series)
etc...

Question 7

Auger electron

Answer 7

• Energy from one electron transitioning to lower shell is transferred to orbital electron, which is ejected (instead of characteristic x-ray)
• fluorescent yield = prob that e- ‡ will yield char x-ray, decreases with increasing atomic number (Z)

Question 8

Electron rest energy

1 amu energy

Answer 8

e- = 0.521 MeV
amu = 900 MeV ?

Question 9

Atomic number vs.

Mass number

Answer 9

atomic number (Z) = # protons
mass number (A) = # nucleons (protons + neutrons)
N = # neutrons

Question 10

Isotopes
Isotones
Isobars
Isomets

Answer 10

Isotopes- same # protons
Isotones- same # neutrons
Isobars- same #
Isomers- different energy state

Correct this card

Question 11

Nuclear binding energy

Answer 11

aka mass defect

nuclear mass less than sum of individual nucleons

Question 12

Interactions of charged particles with matter

Answer 12

• Excitation
• Ionization ( e- emitted called delta ray)
• Radiative interactions (Bremsstrahlung)

Total Bremsstrahlung emission is proportional to E_k * z^2 / 820

Question 13

Neutron interactions

Answer 13

Recoil particle?

Nuclear fusion or fission

Question 14

X-rays and gamma rays can interact with atoms in 5 ways

Answer 14

1- Rayleigh scatter
2- Compton scatter
3- Photoelectric absorption
4- Pair production (not with medical imaging)
5- Pass through freely

Question 15

Rayleigh scatter

Answer 15

Elastic, no E loss

Gives off same freq photon but deflected

Question 16

Compton

Answer 16

E- and lower freq photon emitted

Question 17

Photoelectric effect

Answer 17

Interact with loosely bound

Question 18

MR SNR =

Answer 18

Bandwidth

Question 18

PE vs Compton

Answer 18

Both release e- and photon:

• Compton interacts with loose e-
• PE w tightly bound
• Compton incident photon loses energy
• PE inc photon absorbed, characteristic x-ray released