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Rad 520 Physics > Photon Interactions > Flashcards

Photon Interactions Flashcards

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1
Q

What is the energy level for coherent interaction

A

< 10 Kev

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2
Q

Coherent interaction is dependent on what?

A

High Z

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3
Q

Photoelectric effect is dependent on?

A

Z^3 / E^3

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4
Q

What is the energy level for photoelectric

A

60-90 Kev

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5
Q

what is Compton dependent on?

A

Independent of z #, depends on elector density

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6
Q

What energy level does Compton happen at?

A

25 Kev - 10mev

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7
Q

What energy does pair production happen at?

A

> 1.02 MeV

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8
Q

Pair production is dependent on?

A

Z^2

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9
Q

Coherent occurs at -??

A

Low energy & high Z

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10
Q

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

A

Coherent

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11
Q

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

A

Coherent scatter

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12
Q

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

A

Coherent scatter

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13
Q

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

A

Photoelectric effect

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14
Q

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

A

Photoelectric effect

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15
Q

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

A

Less of refraction angle

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16
Q

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

A

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

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17
Q

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

A

Compton effect

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18
Q

Interaction where binding energy is less than incoming energy of photon

A

Compton effect

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19
Q

Electron density decreases slowly with

A

Increase in atomic number

20
Q

Compton effect is dependent on

A

Electron density

21
Q

Dominate interaction for rad therapy?

A

Compton effect

22
Q

Compton effect: radiation that scattered at right angle energy?

A

0.511 meV

23
Q

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

A

O.255 meV

24
Q

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

A

Pair production

25
Q

Threshold for pair production

A

1.02 meV

26
Q

Likelyhood of pair production increases with

A

Z ^2

27
Q

Nucleus absorbs a high energy photon (>10 MeV)

A

Photodisintegration

28
Q

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

A

Photodisintegration

29
Q

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

A

mass density

30
Q

When mAS is doubled there is

A

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

31
Q

U/p shows us

A

Mass attenuation coefficient for photoelectric Compton and pair production combined

32
Q

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

A

Elastic collision

33
Q

Some kinetic energy is lost to excitation, ionization or bremsstrahlung

A

Inelastic collision

34
Q

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

A

Light charged particles: electRons / positRons

35
Q

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

A

Heavy charged particles: protons, alpha particles - heavy nuclei

36
Q

Electrons interact w matter similar to

A

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

37
Q

Electrons lose energy by______&_________?

A

Collisional & radiative means

38
Q

Electron interacts w/ another electron in matter

A

Collisional

39
Q

Electron interacts with/ a positively changed nucleus in matter

A

Radiative

40
Q

Stopping power of election

A

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

41
Q

Best absorbers for Neutron interactions

A

Hydrogenous materials (not high Z material )

42
Q

Biological effects of radiation result primarily in damage to DNA

A

Direct radiation

43
Q

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

A

Linear energy transfer (let)

44
Q

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

A

Indirect acton

45
Q

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

A

Free radical

Rad 520 Physics (5 decks)

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