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116 Cards in this Set
- Front
- Back
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what is excitation
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when an atomic electron is raised to a higher energy state, even though it is still held by the atom. it will eventually fall back to original state by emitting optical radiation or heat
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what is ionization
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when an electron is ejected from an atom. undergoes interactions similar to the primary electron
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elastic collision
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energy is conserved the same way KEp=KEs
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inelastic collision
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sum of kinetic energy of the particles is changed form but total energy is the same KEp=KEs+KEdr
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specific ionization def.
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the number of primary and secondary ion pairs produced per unit path length of incident radiation
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SI
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specific ionization
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SI of alpha particle in air
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30,000-70,000 ip/cm
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SI of electron in air
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60ip/cm
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LET
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liner energy transfer
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Linear energy transfer def.
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average energy lost per path length
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LET formula
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LET=SI x W
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W def.
and value |
average energy expended to produce an ion pair in air
33.97eV |
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LET depends on ___ and ___
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energy and charge of a particle
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as charge increases,
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LET increases
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as energy or velocity increases
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LET decreases
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Range def
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straight line distance transversed by the particla before it is completely stopped
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Range formula
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range =energy/LET
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da
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10^1
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h
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10^2
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k
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10^3
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M
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10^6
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G
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10^9
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T
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10^12
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P
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10^15
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E
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10^18
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Z
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10^21
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Y
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10^24
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d
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10^ -1
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c
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10^ -2
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m
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10^ -3
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u (mew, looks like m)
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10^ -6
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n
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10^ -9
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p
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10^ -12
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f
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10^ -15
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a
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10^ -18
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z
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10^ -21
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y
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10^ -24
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prefixes ending in "o" typically means
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negative
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photons and other heavy charged particles also exibit___SI and ___ range
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HIGH SI and SHORT range
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alpha particles and protons have a charge of
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+2
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u (mew, looks like m)
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10^ -6
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n
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10^ -9
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p
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10^ -12
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f
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10^ -15
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a
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10^ -18
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z
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10^ -21
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y
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10^ -24
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prefixes ending in "o" typically means
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negative
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photons and other heavy charged particles also exibit___SI and ___ range
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HIGH SI and SHORT range
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alpha particles and protons have a charge of
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+2
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compared to alpha particles, electrons are _______
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sparsely ionizing
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name 2 types of interactions for electrons
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1. collisions
2. radiation losses |
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electron interaction: collision means
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electron interacts with an atomic electron
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electron interaction: radiation losses means
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electrons interacts with a nucleus of an atom
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probability of collisional interaction increases with
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increasing atomic number (z) of absorber
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probability of collisional interaction decreases with
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increasing kinetic energy of the incident electron
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bremsstrulung
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a photon that appears from energy loss (e- goes around nucleus and loses energy)
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probability of radiation losses increases as
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atomic number of absorber increases
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when a positron combines with a free elecron and gives off 2 photons
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positron annihilation
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significance of E=mc2
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can convert mass into energy and energy into mass
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what do we want for specific activity?
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large output/activity in a small volume
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neutron interactions:
Thermal intermediate fast high energy |
thermal= -<.5ev
intermediate= -.5eV to 10 keV fast=->10keV high=>10Mev |
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sources of neutrons
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cyclotron, reactor, 252Cf, neutron generator
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what happens below 3MeV
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elastic scattering, neutron collides with a nucleus and is scatterwred with a loss of evergy
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what happens at energy greater than 10Mev interacts with atomic number greater than 25?
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inelastic collisions, neutron enters nucleus and then exits with reduced energy , gives off gamma ray
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radiativecapture
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occurs with thermal neutrons,
neutron is captured by nucleus to form comput nucleus with emissionof gamma ray |
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used as a method of stopping thermal neurons
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radiative capture
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why we don't use neutrons to treat
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produce greater damage
bounce around the room irradiate other parts of patients |
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bombardment of certain high atomic number materials by neutrons
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fission
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bremsstruhlung aka
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white, continuous, breaking radiation
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what is an xray
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an extremely short wavelength eletromagnetic radiation
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two types of xrays
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1. bremsstralung
2. characteristic radiation |
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how is bremsstralung produced?
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high KE e- approaches nucleus with a strong Coulomb attraction
gets deflected by the nucleus causing the e- to lose energy lost energy appears as a photon |
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close e- gets to nucleus
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more energy is lost
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prob. of bremsstrulung increases with
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the energy of the electron
increases as the z of the targets increases |
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efficiency of x-ray production equation
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efficiency= (output energy emitted as x-ray)/(input energy deposited by electron)
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efficiency=
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efficiency= z x V x 9 x 10^ -10
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below 100keV xrays are emitted
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equally in all directions
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t/f:
e- are the ONLY particle to give a bremsstrulung? |
TRUE
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as energy increases x-rays are emitted
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in a more forward direction
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1/2 of Radium
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Rd=1622yrs
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1/2 of Radon
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Rn=3.8 days
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1/2 life of Cs
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Cs=30yrs
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1/2 life of Co60
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5.26 yrs
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1/2 life of Iodine
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60 days
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1/2 of iridium
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Ir =74 days
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1/2 of P32
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14 days
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1Angstroms=
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1A=10^ -10m
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c=
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c=(lambda) x v
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speed of light
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3x10^8m/sec
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E=
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E=12,400/ (lambda in angstroms)
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quantity of charge for an electron
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1.6x10^ -19C
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quantity of charge for an proton
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1.6x10^ -19C
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mass: electron energy =
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0.511MeV
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gravity
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9.8m/sec2
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t/f:
the charge of an e- is 1.6x10^ -19? |
TRUE
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the ______ of charge carried by and e- is carried by the Coulomb
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quantity
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period=
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period=sec/cycle
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frequency=
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1/period, or cycles/sec
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t/f:
photons have a singular energy? |
TRUE
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how many 1/2 lifes does it take to dicipate radiation
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10
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what is emitted from the nucleus during decay?
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gamma ray
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characteristic properties of a radoactive nuclide
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1. mode of decay
2. transition energy 3. 1/2 of parent |
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why is p32 unusual in decay?
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doesn't emit a gamma ray in its beta decay
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atom =___in diameter
nucleus=____in diameter |
atom=10^ -10
nucleus= 10^ -14 |
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T/F:
as the temperature decreases so does the resistance to current flow? |
TRUE
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t/f
a radioactive nucleus increases its proton number by beta minus decay |
true
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t/f
electron capture will sometimes occur as a decay process instead of internal conversion? |
False
it is not a decay process just something that happens |
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what is a nucleon
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made up of protons and neutrons
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1Ci=
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3.7x10^ 10dps
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as (lambda) increases, v__
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decreases
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1Bq=?dps
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1Bq=1dps
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the same___ of atoms decay in a give time not the same ___ of atoms
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same proportion decays in a given time, not the same number of atoms
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how much energy is needed to break up a nucleus?
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127.5MeV
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decay constant equation
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decay constant= change in N/ change in time
or -(lambda)xN |
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1/2 equation
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t1/2= .693/ #yr
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