Physics Exam 3 & 4 (Final)

In an Bohr model, what is inside of the nucleus?

protons and neutrons

1 unit of charge =

1.6 x 10^-19 Coulombs

if we apply enough energy equivalent to the binding energy of the electron, we can cause what

the electron to be emitted

electron volt

unit of energy; very low compared to the use of joules

atomic mass unit (dalton) is

one twelfth the mass of a carbon-12 atom

Atomic mass unit is equal to what number?

1.6605x 10^-27 kg

What does the number 12 represent in this picture? (Top number next to the element carbon)

12 represents the mass number of the element (number of protons and neutrons)

What does the number 6 represent in this picture? (Bottom number next to the element carbon)

6 represents atomic number (number of protons)

nuclear binding energy define

the energy required to decompose an atomic nucleus into its component protons and neutrons

mass defect

mass defect is the mass equivalent of the binding energy

nuclear binding energy equation (albert einstein's equation)

E=mc^2

E= energy in joules

M= mass kg

C= velocity of light in a vacuum 2.998x 10^8

1 amu is equal to

931 MeV

Isotopes have the same number of ______but different number of _________

proton number; atomic and neutron number

Isotopes are dealing with the same ______

element

isostones have the same number of ______ but different number of _________& ______

same number of neutrons but different atomic and mass number

isobars have the same number of ______ but different number of _________& ______

same mass number but different atomic number and number of neutrons

Which nuclear configuration has the same atomic, mass, and neutron number?

isomers

what makes something radioactive?

The neutron to proton ratio is too high or too low, and therefore the nucleus is unstable and will become radioactive

Beta particles are

the same thing as an electron except is resides outside of the nucleus

disintegration define

an unstable atom that reconfigures itself to become stable again

dps is an abbreviation for

disintegration/sec

1 dps is the same thing as a

Becquerel (Bq)

Curie (Ci) equals what number

3.7x10^10 dps

Half Life (T½) define

transformation of a disintegration for the time it takes for the transformation to occur (that it takes 50% of the atoms to decay)

Decay constant (λ) is

λ= 0.693/t 1/2

half life equation

A= λxN

A= activity in Bq/dps

λ = 0.693/t 1/2

N= # of atoms

Decay Formula

A= Aoxe^ -λT

Ao= original activity

λ = decay constant

T= elapsed time

e = a number

physical half-life define

half-life of a substance as it sits on a shelf in vial

biological half-life

when we take into account that we "leak" (urine,sweat) which makes us not a perfect vial, thus eliminating the radio nuceide in other ways

Teff = (formula)

T½ phys x T½ bio/ T½ phys + T½ bio

Secular Equilibrium

half life of the parent is much more greater then the daughter

relative daughter activity

decreases and appears to decay with the longer half-life

transient equilibrium

If the half-life of the parent is not much longer than that of the daughter.

beta emmiters

occurs when the proton and neutron ratio is too high; occurs for atomic number is less then 82

radioactivity is determined by the

arrangement/ratio of protons and neutrons in the nucleus

Alpha particles are

consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. They are generally produced in the process of alpha decay

alpha emission define

occurs when the proton and neutrons ratio is too low, only occurs for atomic numbers greater than 82

What is the equation for binding energy

Q= Mp - Md - M alpha - 2Me -

Q = Total energy released

M = mass

P = parent

d = daughter

e = electrons

Explain what happens during a decay scheme

energy transitions from parent to daughter as a function of the atomic number; meaning the atomic number will go down and to the left on periodic table

Beta particles occur how?

when the neutron and proton ratio is too high, making the nucleus unstable

Neutrino define

negative charge that are so small that they go right through matter

What type of energy is shared by neutrino and a beta particle?

maximum energy

mean energy is what fraction of the Emax?

1/3 of the Emax

Positrons

have the same mass as an electron but are positively charged; neutron to proton ratio is too low with lower atomic masses

annihilation radiation define

when the beta + collides with a free electrons, it will convert into energy, photons in the form of two 5ll Kev are emitted that are 180 degrees apart

electron capture

When the neutrons to proton ratio is too low to add an electron so they pull an electron into the nucleus to form another neutron

Electron capture puts the nucleus into an excited stage to produce what?

gamma ray

electromagnetic waves

when we get too high of a frequency waves, they penetrate like gamma and characteristic waves

photon

a particle of electromagnetic radiation having zero mass and carrying a quantum of energy

2 types of electromagnetic radiation

1. Gamma rays

2. x-rays

Gamma rays define

emitted from an excited nucleus following radioactive decay

X-ray definition

form of electromagnetic radiation similar to visible light but shorter in wavelength

short wavelength

What is a metastable state?

A metastable state is a long-lived excited state that is longer than the ordinary excited state but has a shorter lifetime than regular ground state.

What are the 2 types of x-rays?

1. characteristic x-rays

2. Bremsstrahlung x-rays

Characteristic x-rays define

Electrons that drop down from shells towards the nucleus and give off characteristic x-rays

Bremsstrahlung x-rays

Beta particles approaches the nucleus and is accelerated redically, emits braking x-rays as it moves outward occur when charged particles are interacting with matter as projectiles

how do you minimize the charged particles in a x-ray

using a material that has a low atomic number

How do maximize the production of x-rays?

using materials with high atomic masses

Auger electron

When an outer shell electron is kicked out of an atom; emitted instead of a characteristic x-ray occasionally

conversion electron

rather than having a gamma ray emitted the energy is transferred to an orbital electron and that electron is what gets released

When does ionization occur?

when an incident photon interacts with orbital electron and imparts a sufficient amount of energy to expel it from the atom

ionizing potential define

amount of energy required to ionize the least tighly bound electron of an atom

Linear Energy Transfer (LET) define

average energy deposited per unit half-length traveling by incident radiation; how much is lost per unit

Why is LET not an accurate measruement?

Because it only takes the average . The only thing that it is good for is seeing high vs low radiations

High LET =

alpha; 7,200 times bigger than beta particles; loses lots of energy in a short range, meaning it does not go very far

Low LET =

everything else such as Beta, gamma, x-rays

Pair production

a photon that is greater than or equal to 1.02 MeV

Half value layers only stay consistent for ______

monoenergetic

State why a positron will not exist naturally on its own for a long period of time

because it will annihilate a free electron and produce two 511 Kev 180 degrees

Compton scattering define

moderate energy photon, photon interacts with an electrons that has a binding energy much lower than the incident photon (outer shell electron) and ionize it

Lower energy photons

photoelectric absorption (because compton scattering energy has become less and less energy)

What are the 2 critical restrictions of radiation exposure?

1. only in air

2. only from electromagnetic radiation such as gamma and x-rays

Common unit and SI unit for radiation exposure

common unit: Roentgen (R)

SI unit: Columb/kg

Absorbed dose definition

any type of radiation in any medium; no restrictions

absorbed dose common and SI units

Common units: Rad = 100 engs/g

SI units: gray (gy) = 1 J/K

- 1 gy = 100 rad

Equivalent dose define

considers both the quantity and quality of radiation in people; only measured in living people

Equivalent dose formula

absorbed dose x quality factor (QF) = equivalent dose

QF for alpha dose =

20

QF for gamma, x-rays, and beta =

1

Common unit and SI unit for QF

Common unit: Rem

SI unit: Sievert (sv)

- 1 sv = 100 rem

2 methods to calculate radiation exposure

1. Gamma constant: getting R/hr to cancel

R * cm^2/mCi * hr

2. Exposure rate: if we do not know gamma's constant

x( at 1 ft) = (6)*(curies)*(MeV)

Inverse square law

This is used to calculate the exposure rate at a different distant

Formula: I1D1^2 = I2 D2^2

Half value layer

thickness of a shield that will attenuate 50% of the beam; probability that 50% is getting shielded

Half value layers only stay consistent for ____

monoenergenic

Patients are more likely to do what with lower energy x-rays?

Absorb the x-rays, making the images not clear

Low energy x-rays are more likely to be _____ causing what to happen?

Shielded; causing the energy exiting to be disproportionate

Allowing higher energy x-rays to come out, does what for the diagnostic image and the patient?

helps minimize the radiation dose to patient and to get the clearest diagnostic image

Formula(s) for half value layer

I = Ioe^-mx

M = 0.693/HVL

X= thickness of shield

OR

I = Io/2n

n = # of HVL

What is the info that we need to know to figure out how much shielding we need for an x-ray room (Diagnostic x-ray sweeps)

1. Max Kvp = highest energy coming off

2. Max mA = maximum current in milliamps

3. Workload: how much time in a given week will that tube be energized : mA* min/week

4. use factor (u): have to configure the % of each wall of the room that will get hit by a beam: 6 walls to be considered

5. Occupancy Factor (T): knowing whats on the other of the room; we need a floor plan to see where everything is at

Restricting areas for radiation

greater than or equal to 2 mR/hr; controlled access or shield it.

No posting required means

We won't have to put up a sign if it is under 5 mR/hr.

What is the range of radiation that is required to put up a "caution radiation area" sign?

If it is greater than or equal to 5 mR/hr but less than 100 mR/hr

If the radiation is above 100 mR/hr, what sign would you put up?

"caution High Radiation area"

When would you need to put a "Caution, radioactive materials" sign up?

if you have any sort of radioactive materials in a room; restricted so people who are not trained in radioactivity cannot access them.

Dose Limit: General Public

100 mrem/year

Deep dose equivalent (DDE)

whole body dose, 1 cm deep into skin

5,000 mrem/year

why do you wear a dosimeter at the collar?

Because if you wear a lead apron, your neck and face are not covered. So you must track how much radiation is getting onto your skin neck up.

Lens dose equivalent (eye dose) limit

15,000 mrem/year in United States

Shallow dose equivalent (SDE)

50,000 mrem/year; skin dose equivalent

Extremity dose equivalent

Knees and elbows down: 50,000 mrem/year