Nuclear Flashcards
charge on proton/electron (not exact coulombs)
1e
alpha decay equation and process
helium nucleus (2p, 2n)
mass number down by 4, atomic number down by 2
beta decay equation and process
- a electron or positron given off
- neutron turns into proton or vice versa
- mass number same, atomic number one up or one down
- anti neutrino for -, neutrino for +
Ionisation
Penetration
Stopped By
Alpha, Beta, Gamma
Ionisation: high, mid, low
Penetration: low, mid, high
Stopped By: paper, aluminium, lead
uses of three radiations
alpha: smoke detector
beta: paper thickness gauge
gamma: sterilising, radiotherapy
What is gamma radiation
nucleus does not change
gets rid of spare energy
Decay constant in radioactivity
λ
probability of a nucleus decaying in the next second
Bq
number of decays per second
Half life meaning
time taken for radioactive activity to half
Activity, decay constant, number of undecayed nuclei left
A = λN
ratio of activity, mass, number against time and decay constant
A/A0 = M/M0 = N/N0 = e^-λt
half life equation
t = ln(2)/λ
where t is half life
time constant meaning (2)
time when we have 37% of original value
(1/e)
when λt = 1
time constant, decay constant
tc = 1/λ
where tc is time constant
measured activity / true activity
when a small detector is measuring count from a central gamma source
measured activity / true activity
Area of detector/4πr^2
intensity from radiation source
intensity = radiation/area
I = k/4πr^2
intensity, distance realstionship
I ∝ 1/r^2
I1r1^2 = I2r2^2
- if detector moved x3 far away, intensity down by 1/9
parts of a fission reactor and purposes
- coolant - remove heat from core
- fuel rods
- moderator - slows down neutrons to increase fission (eg. water)
- control rods - absorbs some neutrons to reduce chain reaction (eg. boron)
what they do with radioactive waste
vitrify and bury
where Fusion happens
sun
H- bombs
unit of relative atomic mass
1u
mass of constituents vs mass of nucleus
mass of constituents > mass of nucleus
mass defect
change in mass from nucleus constituents to nucleus
converted to energy
binding energy
energy required to separate a nucleus/atom into its constituents
energy, mass
E = Δmc^2
where mass is in kg
1u to kg
1u = 1.67 x 10^-27 kg
u to MeV
x 931.3
1 MeV to joules
1 MeV = 1.6 x 10^-13 J
binding energy change in fission and fusion
- total binding energy increased
- mass lost
what makes nucleus stable (binding energy)
binding energy per nucleon increases
cone of stability and where types of radiation happen
- stability cone above N = Z
- B- above
- B+ below
- alpha top corner
Rutherford scattering setup
- alpha transmitter
- gold foil
- detector that can co all the way round
Rutherford scattering results and conclusions
Results
- most alpha particles passed straight through foil
- few deflected by >4
- very few deflected by >90
Conclusions
- atom is mostly empty space
- concentration of positive charge in atom
- nucleus has high density and mass
electrical potential energy equation
Ep = Qq/4πε0r
where Q and q are the two charges
r is distance of separation
find closest approach to approximate radius of nucleus
initially Ek = 1/2 mv^2
at point of repulsion, all Ek into Ep
Ep = (2e)(Ze)/4πε0r
1/2 mv^2 = (2Ze^2)/4πε0r
r = (Ze^2)/πε0mv^2
