Radioactivity Flashcards
What is alpha radiation
consists of positively charged particles. Each alpha particle is a helium nucleus with 2 protons and 2 neutrons and has charge +2e
What is beta radiation
fast moving electrons (for beta-) or fast moving positrons (for beta+). Charges -e and +e respectively
What is gamma radiation
high energy photons in an electromagnetic wave of wavelengths less than 10^-13.
how to alpha particles act
- high ionisation
- low penetration
- stopped by air or paper
how to beta particles act
- medium ionisation
- medium penetration
- stopped by a sheet of aluminium
how to gamma particles act
- no charge
- low ionisation
- absorbed by lead
why is radioactive decay random and spontaneous
random because can’t predict when each nucleus will decay and which one will decay
spontaneous because not effected by external factors
Define half life
average time taken for half the number of active nuclei in the sample to decay
Equation to find decay constant
A = λN or ΔN/Δt=-λN
define the decay constant
probability of a nuclei decaying per unit time
what equation to use when asked about change in energy when referring to mass changes, within decay equations, also binding energy
einstein’s mass energy equation
define mass defect
difference in mass of the nucleus and the combined mass of the same completely separated nucleons
define binding energy
minimum energy required to completely separate a nucleus into its constituent protons and neutrons
outline significant parts of the binding energy per nucleon graph
- axis are binding energy per nucleon against nucleon number
- fusion occurs up to iron
- fission occurs from uranium back to iron
describe the structure of a fission reactor
- Fuel rods containing uranium are evenly spaced within a steel concrete reactor core
- A coolant is used to remove the thermal energy produced from the fission reactions
- Control rods made of boron absorbs nucleons
- moderator slows down fast paced neutrons, heavy water
