Please enable JavaScript.
Coggle requires JavaScript to display documents.
Nuclear Radiation (Decay (Although radioactive decay random, it is…
Nuclear Radiation
Decay
Nuclear instability caused by:
- Too many neutrons
- Too few neutrons
- Too many nucleons (too heavy)
- Too much energy in nucleus #
Alpha Particles:
- Helium nucleus
- Charge +2
- Mass 4u
- Strongly ionising due to strong positive charge to pull electrons from atoms
- Low speed as relatively heavy
- Low penetration (paper or few cm of air) as quickly ionises a lot of atoms and so loses energy quickly
- Affected by a magnetic field
-
Beta-Minus
- Electron
- Charge -1
- Negligible mass
- Weakly ionising due to weaker charge
- Fast speed due to lower mass
- Higher penetration (≈ 3mm aluminium) as less ionisations so lose less energy
- Affected by magnetic field
-
-
Beta-Plus
- Positron
- Charge +1
- Negligible mass
-
Proton changes to neutron, releasing positron (beta-plus particle) and neutrino
Gamma
- Short wavelength, high frequency EM wave
- No charge
- No mass
- Very weakly ionising as has no charge or mass
- Travels as speed of light
- Strong penetration (many cm lead, several m concrete) as few ionisations means little energy loss
- Not affected by magnetic field
Gamma radiation emitted by nuclei with too much energy (excited nucleus) - energy lost by emitting gamma ray - often happens after beta/alpha decay
Decay equations must balance for charge, nucleon number, energy and momentum - but not mass - difference accounted for by mass defecit
Although radioactive decay random, it is possible to predict how many nuclei will decay in a given time
-
-
-
-
t(1/2) = half life = average time taken for number of undecayed nuclei to halve (in practise - for count rate to halve)
Fusion
-
Lots of energy released as new heavier nuclei have a much higher BE per nucleon - helps maintain temperature for further fusion reactions
-
Conditions:
- ≈ 1MeV KE
- High density of matter to increase likelihood of collisions between nuclei
- High temperatures
- High pressures
Radiation
-
-
Sources of Background Radiation:
- AIR: Radon gas from rocs emit alpha radiation
- GROUND AND BUILDINGS: all rock contains radioactive isotopes
- COSMIC RADIATION: particles from space collide with those in upper atmosphere
- LIVING THINGS: contain carbon - carbon-14 radioactive
- MAN-MADE: e.g. medical/industrial sources
-
