Radiation Flashcards
Describe the properties of alpha particles
- heavily ionizing
- short range travel (10cm in air)
- can be stopped by a thin card
What are beta particles?
Fast moving electrons ejected from an unstable nuclei
Describe the properties of beta particles
- less ionising than alpha
- travel long distances in air
- stopped by 1-2mm of aluminum
What are gamma rays?
Photons of high energy electromagnetic waves
Describe the properties of gamma rays
- very penetrating
- interact with atoms which way emit ionising radiation
- stopped by tens of cm of lead
Describe what happens to an element that undergoes alpha decay
loses 4 in atomic mass, 2 in atomic number
Describe what happens when an isotope undergoes beta decay
gains one electron; atomic number increases by 1
How can photographic film be used to detect ionising radiation?
- becomes fogged when exposed to ionising radiation
- used in bagels worn by workers at risk from continuous exposure
- badges regularly checked to ensure safety limits haven’t been exceeded
How can the Geiger-Muller tube be used to detect ionising radiation?
- ionising radiation enters the tube
- ionises the gases to allow a pulse of current to pass between electrodes
- fed into counter
What are alpha particles?
Helium nuclei ejected from an unstable nuclei
List some sources of background radiation
- radon gas (50% of total background radiation)
- rocks
- buildings
- cosmic rays
- x-rays/radiotherapy
- coal power/nuclear power stations
- food and drink (potassium)
Define half-life
The amount of time it takes for half of undecayed nuclei to decay
Not dependent on sample size, only on the type of isotope
Iodine-131 has a half life of 8 days. How much of an initial sample of 400ug would remain after
a) 16 days
b) 24 days
c) 80 days
a) 100ug
b) 50 ug
c) 0.39 ug
Explain how radioactive tracers can be used in medicine
- chemicals containing gamma emitters can be swallowed or injected
- follow transport of tracer through digestive system or veins and arteries
- some compounds chosen because they’re concentrated in particular organs
- allow structure and function of organs to be examined closely
Explain how radioactive compounds can be used to treat illnesses
- iodine-131, beta emitter, taken orally to treat conduit of thyroid gland
- iodine is concentrated in the thyroid
-radiation kills off cells
or - focused beams of gamma rays can kill off cancerous cells in tumours
describe how carbon dating works
- carbon 14 is absorbed by all living things during respiration
- proportion of carbon 14 to carbon 12 reduces at a predictable rate after death
why is radioactivity hazardous to humans
- ionization disrupts the genetic material in a cell
* cell starts to malfunction and reproduce uncontrollably, producing a tumour- cell mutation
how can you make sure no radiation escapes
lead or concrete
what does the amount of deflection of alpha particles depend on
speed
nuclear charge
how close they get to the nucleus
define fissile
can split into lighter elements easily
what happens in nuclear fission
if an atom of U-235 is struck by a low energy neutron
it becomes unstable and splits into two daughter nuclei, three neutrons, and gamma radiation
define a nuclear bomb in terms of nuclear fission
uncontrolled chain reaction
how can you generate electricity from nuclear fission
if the chain reaction is controlled to make the energy release more slowly, the heat can be used to
generate steam
to turn turbines
and drive generators
what is a graphite moderator used for in electricity generators wit nuclear fission
absorb some of the energy of fast neutrons
to sustain the chain reaction
why do you need boron control rods
absorb neutrons to take them out of action completely
can be raised out of reactor core to speed up reaction
lowered completely to shut down chain reaction
describe how a smoke detector work
has an ionization chamber with a small radioactive source that my produces alpha particles;
alpha particles ionize oxygen molecules and hence enable a current to pass between charged plates in the chamber;
when smoke enters, it absorbs and neutralizes oxygen ions, makes current fall;
change in current is detected, sets off an alarm
