Photon Interactions

Question 1

What is the energy level for coherent interaction

Answer 1

< 10 Kev

Question 2

Coherent interaction is dependent on what?

Answer 2

High Z

Question 3

Photoelectric effect is dependent on?

Answer 3

Z^3 / E^3

Question 4

What is the energy level for photoelectric

Answer 4

60-90 Kev

Question 5

what is Compton dependent on?

Answer 5

Independent of z #, depends on elector density

Question 6

What energy level does Compton happen at?

Answer 6

25 Kev - 10mev

Question 7

What energy does pair production happen at?

Answer 7

> 1.02 MeV

Question 8

Pair production is dependent on?

Answer 8

Z^2

Question 9

Coherent occurs at -??

Answer 9

Low energy & high Z

Question 10

Interaction when a photon passes near an electron & sets it into a oscillation.

Answer 10

Coherent

Question 11

The electron then gives Off the same energy at the same frequency as the incident photon.

Answer 11

Coherent scatter

Question 12

Interaction where a photon passes near an e- and sets it into an oscillation.

Answer 12

Coherent scatter

Question 13

Photon Interaction with an inner electron & ejects one the of orbital elections

Answer 13

Photoelectric effect

Question 14

Interaction where a photon interacts with a inner electron & emits an electron & can produce characteristic xrays or auger electron

Answer 14

Photoelectric effect

Question 15

With photoelectric effect as photon energy increases what happens to ejected electron

Answer 15

Less of refraction angle

Question 16

What would be the probability of photoelectric effect when transitioning from a tungsten target to a molybdenum target

Answer 16

Molybdenum^3 / tungsten^3 ( decrease as target Z decreases )

Question 17

An incoming photon hits an outer orbital electron & not all energy is transferred. This results in an ejected electron and a weaker photon.

Answer 17

Compton effect

Question 18

Interaction where binding energy is less than incoming energy of photon

Answer 18

Compton effect

Question 19

Electron density decreases slowly with

Answer 19

Increase in atomic number

Question 20

Compton effect is dependent on

Answer 20

Electron density

Question 21

Dominate interaction for rad therapy?

Answer 21

Compton effect

Question 22

Compton effect: radiation that scattered at right angle energy?

Answer 22

0.511 meV

Question 23

Compton effect: radiation scattered at 180° (backscatter) energy

Answer 23

O.255 meV

Question 24

An incoming photon interaction with the nucleus & gives up all its energy in creating a position and a negatron -

Answer 24

Pair production

Question 25

Threshold for pair production

Answer 25

1.02 meV

Question 26

Likelyhood of pair production increases with

Answer 26

Z ^2

Question 27

Nucleus absorbs a high energy photon (>10 MeV)

Answer 27

Photodisintegration

Question 28

Energy causes nucleus to eject a particle, therefore changing its nucleon #

Answer 28

Photodisintegration

Question 29

Quantity of Matter per unit volume (kg/m^3)

Answer 29

mass density

Question 30

When mAS is doubled there is

Answer 30

Twice the probability of interaction as there are twice as many electrons

Question 31

U/p shows us

Answer 31

Mass attenuation coefficient for photoelectric Compton and pair production combined

Question 32

Total kinetic energy of all particles is the same before & after collision

Answer 32

Elastic collision

Question 33

Some kinetic energy is lost to excitation, ionization or bremsstrahlung

Answer 33

Inelastic collision

Question 34

Follow a zig-zag path as they are easily scattered due to low mass

Answer 34

Light charged particles: electRons / positRons

Question 35

Follow a straight path, energy lost per unit path length is proportional to square of charge & inversely proportional to velocity

Answer 35

Heavy charged particles: protons, alpha particles - heavy nuclei

Question 36

Electrons interact w matter similar to

Answer 36

Heavy particles, but they scatter much more & change direction more

Question 37

Electrons lose energy by______&_________?

Answer 37

Collisional & radiative means

Question 38

Electron interacts w/ another electron in matter

Answer 38

Collisional

Question 39

Electron interacts with/ a positively changed nucleus in matter

Answer 39

Radiative

Question 40

Stopping power of election

Answer 40

2mev/cm ( loses 2 meV per cm - 10 meV can only penetrate 5 cm )

Question 41

Best absorbers for Neutron interactions

Answer 41

Hydrogenous materials (not high Z material )

Question 42

Biological effects of radiation result primarily in damage to DNA

Answer 42

Direct radiation

Question 43

Measure of the rate at which energy is transferred from ionizing radiation to soft tissue,

Answer 43

Linear energy transfer (let)

Question 44

Radiation interacts w other atoms to produce free radicals that then do the damage to critical targets

Answer 44

Indirect acton

Question 45

Atom or molecule that has an unimpaired orbital electron in the outer shell

Answer 45

Free radical