Radiation Physics - Exam 3

Front 1

What are atoms?

Back 1

fundamental constituents of matter that maintain the properties of that element of matter

Front 2

How are electrons held in place?

Back 2

binding energy (from the nucleus)

nucleus has a positive charge, attracting the electrons and holding them in place

Front 3

What are the 3 units for energy?

Back 3

joules
erg
eV

Front 4

What does the value of an atom's binding energy tell you?

Back 4

the value of an atom's binding energy is the amount of energy that it would take to completely remove the electron from the atom

Front 5

What determines an atom's chemical properties?

Back 5

its electron configuration

Front 6

What determines an atom's stability?

Back 6

its nuclear configuration

remember:
stable means not radioactive
unstable means radioactive

Front 7

An atomic mass unit is a way to discuss the mass of an atom.

How do we describe an amu?

Back 7

an amu is equal to 1/12 the mass of a C-12 (carbon 12) atom

or

1.6605 x 10^-27 = 1 amu

Front 8

Z stands for an atom's

a. mass number
b. atomic number
c. number of neutrons
d. number of electrons

Back 8

atomic number
(which is the number of protons)

Front 9

A stands for an atom's

a. mass number
b. atomic number
c. number of neutrons
d. number of electrons

Back 9

mass number
(which is the number of protons + neutrons or the number of "nucleons")

Front 10

True or False:
Isotope means radioactive.

Back 10

False.

An isotope of an element is one that has the same number of protons but a different number of neutrons.

Front 11

What principle does electrostatic force refer to?

What works against the electrostatic force an atom's nucleus?

Back 11

like charges repel


strong nuclear force works against & exceeds the electrostatic force by ~100x

Front 12

What does mass defect mean?

What does it represent?

Back 12

the mass of the parts is greater than the mass of the whole

it represents the mass equivalent of the amount of energy that must be applied to separate the nucleus into its individual components

Front 13

What is the speed of light in a vacuum?

Back 13

3x10^8 m/sec

Front 14

1 amu = how many MeV?

Back 14

1 amu = 931 MeV

Front 15

What is the formula for nuclear binding energy?

Back 15

nuclear binding energy = (mass defect in amu) x (931 MeV)

gives you nuclear binding energy in MeV

Front 16

An ISOTOPE of an atom has what in comparison to the atom's atomic number, mass number, and number of neutrons?

Back 16

same atomic number
different mass number
different number of neutrons

Front 17

An ISOTONE of an atom has what in comparison to the atom's atomic number, mass number, and number of electrons?

Back 17

different atomic number
different mass number
same number of neutrons

Front 18

An ISOBAR of an atom has what in comparison to the atom's atomic number, mass number, and number of neutrons?

Back 18

different atomic number
same mass number
different number of neutrons

Front 19

An ISOMER of an atom has what in comparison to the atom's atomic number, mass number, and number of electrons?

Back 19

same atomic number
same mass number
same number of neutrons

**same element but it is just at a different "state" of excitability <--not sure if we have to know this

Front 20

What is transmutation?

Back 20

1 element changes into another

Front 21

What is disintegration?

Back 21

when a nuclide emits a charged particle

example:

a neutron loses its negative charge to emit a beta particle; this leaves the neutron with a positive charge

Front 22

What are the 3 units for disintegration?

Back 22

dps (disintegration per sec)
Curie (Ci)
Becquerel (Bq) <--SI unit

Front 23

1 Curie (Ci) equals how many dps (disintegrations/sec)

Back 23

1 Ci = 3.7x10^10 dps

Front 24

1 Becquerel (Bq) equals how many dps (disintegrations/sec)

Back 24

1 Bq = 1 dps

Front 25

1 Curie (Ci) equals how many Becquerels (Bq)

Back 25

1 Ci = 3.7x10^10 Bq

(same as dps because 1 dps = 1 Bq)

Front 26

What does half life (T 1/2) measure?

Back 26

the amount of time it takes for 50% of the atom's activity to decay

Front 27

When does the activity of an atom decay to equal zero?

Back 27

NEVER.

decay is exponential - gets closer and closer to zero but never gets there (always taking 1/2 of 1/2 of 1/2)

Front 28

What is the formula for activity?

Back 28

Activity (A) = decay constant x number of atoms (N)

*units for activity will be atoms per unit time but this means atoms disintegrated per unit time

Front 29

What is the decay formula?

Back 29

remaining activity = original activity x e^ - decay constant*elapsed time

Front 30

The decay constant of an atom is equal to what?

Back 30

.693/half life (T 1/2) of the atom

Front 31

If you know the number of half lives that have gone by for a particular atom...

what is the easy way to calculate the remaining activity for the atom?

Back 31

remaining activity = original activity / (2^ # of T1/2 passed)

(remaining activity equals the original activity divided by 2 to the # of half lives that have gone by)

Front 32

What is the difference between physical decay and biological decay?

How does this relate to the effective half life (T-effective or T-eff)?

Back 32

Physical decay is the decay of a radiopharmaceutical as it sits in a vial/bottle/etc. (outside the body); denoted by T-p

Biological decay is the decay of a radiopharmaceutical as it is decaying in the body; denoted by T-b

relation to effective half life:
T-eff = [(T-p) x (T-b)] / [(T-p) + (T-b)]

(effective half life equals the product of T-p and T-b divided by the sum of T-p and T-b)

Front 33

A state of equilibrium means that....

Back 33

the energy radiated is balanced by the energy absorbed

Front 34

Explain secular equilibrium.
(when does it occur & the general idea)

Back 34

occurs when the half life of the parent is MUCH MUCH greater than the half life of the daughter

the activity of the daughter will build up to the activity of the parent and appears to decay with the half life of the parent

Front 35

Explain transient equilibrium.
(when does it occur & the general idea)

Back 35

occurs when the half life of the parent is greater than the half life of the daughter (as opposed to MUCH MUCH greater as seen with secular equilibrium)

the activity of the daughter will build up to the activity of the parent and appears to decay with the half life of the parent (yes - this part is the same as secular)

Front 36

Alpha particles
-mass number?
-atomic number?
-charge?
-mass?

Back 36

mass number = 4
atomic number = 2
charge = 2+
mass = ~4 amu

Front 37

Alpha particle emission occurs when the neutron/proton ratio is

a. too low
b. too high
c. equal

Back 37

the neutron/proton ratio is too LOW

Front 38

All alpha emitters have an atomic number that is ...

Back 38

greater than 82


(there is 1 exception but we do not have to know it)

Front 39

For an alpha particle, what is the formula for total energy released (Q)

Back 39

Q = M-parent - M-daughter - M-alpha - 2M-electron

M = mass

***this formula gives you total energy released in amu - he usually wants the answer in MeV so you will multiply by 931 MeV)

Front 40

What is the formula for the total energy of an alpha particle (Q-alpha)?

Back 40

Q-alpha = Q / [1 + (M-alpha/M-daughter)]

total energy of alpha particle equals total energy released divided by 1 plus the mass of the alpha particle divided by the mass of the daughter

Front 41

What does "monoenergetic" mean?

Back 41

a particular nuclide will always have the same amount of energy


**alpha particles & characteristic x-rays are monoenergetic

Front 42

Beta particles (B-)

- charge?
- "mass number"?
- "atomic number"?

Back 42

charge: -1
mass number: 0
atomic number: -1

Front 43

Beta particle emission occurs when the neutron/proton ratio is...

Back 43

when the neutron/proton ratio is too HIGH

Front 44

For a beta particle, what is the formula for total energy released (Q)?

Back 44

Q = M-parent - M-daughter

M means mass

**because subtracting the M-beta will cancel out with adding the M-electron since they are equal

Front 45

Why is it that beta particles (B-) are not monoenergetic?

Back 45

because when emitted, an anti-neutrino (v) is also emitted

the energy will be divided between the beta particle and the anti-neutrino

Front 46

What is the formula for the average energy of a beta particle (B-)

Back 46

average energy = 1/3 maximum energy

**maximum energy = Q (total energy)

Front 47

A beta particle (B-) is the same thing as an electron except for what one factor?

Back 47

its point of origin is in the nucleus

Front 48

A positron is the same thing as an electron except for what 2 factors?

Back 48

its point of origin is in the nucleus
it has a positive charge (+1)

Front 49

Positrons

- charge?
- "mass number" ?
- "atomic number" ?

Back 49

charge: 1+
mass number: 0
atomic number: 1

Front 50

Emission of positrons (B+) occurs when the neutron/proton ratio is...

Back 50

when the neutron/proton ratio is too LOW

Front 51

All positron emitters have an atomic number that is...

Back 51

less than 82

**since both alpha and positron emission occurs when the neutron/proton ratio is too low, the difference of when each occurs is based on the atomic number

Front 52

For positron particles, what is the formula for total energy released (Q)

Back 52

Q=M-parent - M-daughter - 2M-electron

M means mass

Front 53

What occurs soon after positrons are emitted?

Back 53

annihilation

Front 54

Explain the process of annihilation for a positron particle.

Back 54

A positron attracts an electron.

They collide & explode.

100% of the mass is converted into energy so that you end up with two 511 keV photons that are 180 degrees apart from each other

Front 55

What is electron capture?

Back 55

rather than emitting a particle, an orbital electron is captured

this will occur because the mass of the parent is not enough to "cover" the mass of the daughter
(Q = M-parent - M-daughter would not lead to any energy left to be released)

Front 56

Electron capture occurs when the neutron/proton ratio is....

Back 56

when the neutron/proton ratio is too LOW

Front 57

True or False: No radiation is emitted when electron capture occurs.

Back 57

False.

Electromagnetic radiation will occur when electron capture occurs. ("characteristic x-rays")

Front 58

Explain how electron capture causes characteristic x-rays.

Back 58

An electron gets sucked into the nucleus, leaving a "hole" in the electron shell.

An electron from an outer shell will "drop" to fill the hole.

This gives off an amount of energy that is equal to the difference of the energies between the shells in the form of a characteristic x-ray.

Front 59

Electromagnetic radiation exists in bundles of energy that are referred to as _____.

Back 59

photons

Front 60

What is the formula associated with the dual nature of light?

I didn't really comprehend WTF dual nature of light is so...this card kinda sucks but we do have to know the formula...

Back 60

e = hv

e = energy in Joules

h = planck's constant (value will be given on exam)

v = frequency (use the value of the speed of light in a vacuum 3x10^8 m/sec)

*this gives you the answer in Joules but he may want it in MeV - the conversion for this will be provided

Front 61

What are the 2 types of electromagnetic radiation?

Back 61

1 - x-rays
sub-types:
characteristic x-rays
Bremsstrahlung x-rays

2 - gamma rays

Front 62

Explain how we get Bremsstrahlung x-rays.

Back 62

A beta (B-) particle approaches an atom.

The positive charge in the atom's nucleus attracts the beta particle, causing it to radially accelerate.

The beta particle will lose energy and part of that energy will be converted into Bremsstrahlung x-ray.

Front 63

What is true of the fraction of energy converted into Bremsstrahlung x-rays?

Back 63

the fraction of energy converted into Bremsstrahlung x-rays is DIRECTLY PROPORTIONAL to the atomic number of the medium through which they pass

Front 64

Explain how an Auger electron can be emitted.

Back 64

Electron capture occurs

Electron moves from outer shell in to fill this hole

Energy from this is transferred to an orbital electron, causing it to be emitted (referred to as an Auger electron)

**compared to when the energy goes directly out in the form of a characteristic xray

Front 65

Explain how a conversion electron can be emitted.

Back 65

An atom has a nucleus in an excited state.

Excitation energy is transferred to an orbital electron, causing it to be emitted (called a conversion electron)

**compared to when the energy goes directly out in the form of a gamma ray

Front 66

What is ionization?
What does it create?

Back 66

when incident radiation interacts with an orbital electron and imparts enough energy to expel it from the atom

creates an ion pair (electron expelled is a negative ion, atom remaining is a positive ion)

Front 67

What does the ionization potential of an atom refer to?

Back 67

the amount of energy required to remove the least tightly bound electron from the atom

Front 68

What is excitation?

Back 68

incident radiation interacts with an orbital electron and imparts energy that raises the electron to a higher energy level, but does not impart enough energy to expel it from the atom

Front 69

What does specific ionization refer to?

Back 69

the number of ion pairs formed per unit distance traveled by the incident radiation

Front 70

What does linear energy transfer (LET) refer to?

Back 70

the average energy deposited per unit distance traveled by the incident radiation

high energy deposition corresponds to high LET (losing a lot of energy due to a lot of ionization)

Front 71

Alpha particles are ___ LET while beta particles are ___ LET

(high vs low)

Back 71

alpha - high
*because it has big mass and a double charge

beta - low
*because it is small with a single charge

Front 72

The least penetrating type of particulate radiation are _____ particles.

Back 72

alpha

Front 73

What is an alpha particle's range in tissue?

Back 73

about 1 x 10^-4 cm

Front 74

What are the 3 types of interactions between electromagnetic radiation and matter?

Back 74

pair production
compton scattering
photoelectric absorption

Front 75

What is pair production?

Back 75

direct conversion of electromagnetic radiation to mass

an incident photon with energy greater than 1.02 MeV passes through a nucleus and its energy is converted to mass to yield an electron and a beta particle

Front 76

What is compton scattering?

Back 76

an incident photon with moderate energy interacts with an electron in an outer shell of an atom
the electron is emitted and the photon is scattered

so...
input: photon with moderate energy
output: an emitted electron from a shell and a scattered photon

Front 77

What is photoelectric absorption?

Back 77

a low energy incident photon interacts with an inner shell electron
the electron is emitted

ALL energy from the incident photon is transferred to the electron so there is NO scattered photon in the output

Front 78

What increases the likelihood of the occurance of photoelectric absorption?

Back 78

an absorber with a high atomic number

(this is why lead is a good shield)

Front 79

What is the unit for measuring

-exposure?
-dose?
-equivalent dose?

Back 79

exposure: R (Roentgen)

dose: rad (radiation absorbed dose)

equivalent dose: rem (Roentgen equivalent man)

Front 80

What are the 2 restrictions of measuring exposure?

Back 80

can ONLY be measured in AIR
is ONLY measured for electromagnetic radiation

Front 81

The SI unit for the Roentgen (R) is...

Back 81

1 coulomb/kg of air

*doesn't have a name

Front 82

What does exposure (the Roentgen) measure?

Back 82

the charge generated in the air

Front 83

What does dose (the rad) measure?

Back 83

energy deposited per unit mass

QUANTITY ONLY

Front 84

1 Rad = what?

Back 84

1 Rad = 100 ergs/g

Front 85

What is the SI unit for the rad
What is the conversion between them
Also another conversion to memorize

Back 85

the Gray (Gy)

1 Gy = 100 rads

also know: 1 Gy = 1 Joule/kg

Front 86

How do we find rems?

Back 86

measure dose (rads)
multiply by the quality factor

Front 87

What is the quality factor used when finding rems for an alpha particle? for beta? for gamma? for x-ray?

Back 87

alpha: 20
beta, gamma, x-ray: 1

Front 88

What is the SI unit for equivalent dose (rems)

conversion factor?

Back 88

Sievert (Sv)

1 Sv = 100 Rem