radioactivity Flashcards
what are alpha and beta particles and gamma rays
ionising radiations emitted from unstable nuclei in a random process
describe alpha particles
1) they are helium nuclei
2) they have 2 protons and two neutrons
3) they are big and slow
4) they do not penetrate much
5) they are strongly ionising
6) they have a positive charge so are deflected by magnetic and electric fields
7) emitting an alpha particle decreases the atomic number by 2 and the mass number by 4
describe beta particles
1) they are electrons which are emitted from the nucleus when a neutron turns into a proton and electron
2) when a beta particle is emitted the atomic number increases by 1 but the mass number stays the same
3) they are quite fast and small
4) they penetrate moderately and ionise moderately
5) they are charged negatively so are deflected by magnetic and electric fields
describe gamma rays
1) no mass- just waves with very short wavelengths
2) penetrate a long way
3) weakly ionising
4) no charge
5) gamma emission happens after beta or alpha decay
what is nuclear radiation
causes ionisation by bashing into atoms and knocking electrons off them.
how can you detect ionising radiation
photographic film or Geiger Muller counter
explain the sources of background radiation
1) substances on earth (rocks that give off radon)
2) cosmic rays
3) living things
4) human activity (ie nuclear explosions )
define half life
the time taken for half of the atoms now present to decay
describe uses of radioactivity in industry
1) gamma emitting tracers are used to detect leaks in underground pipes
2) beta radiation used in thickness control (eg paper)
describe uses of radioactivity in medicine
1) treat cancer (kills cells with high concentration of gamma rays)
2) medicine tracers ( beta/gamma source ingested then tracked)
3) food/ equipment sterilisation ( irradiated with high dose of gamma rays to kill microbes)
what is irradiation
exposure to radiation- does not make other objects radioactive
what is contamination
radioactive particles getting onto objects
describe the dangers of ionising radiation
1) can cause mutations in living organisms
2) can damage cells and tissue
3) radioactive waste is hard to dispose of safely
describe how a nucleus of U-235 can be split up (fission)
1) a slow moving neutron is abrored by a uranium-235 nucleus and so the nucleus splits
2) U-235 splits forming two daughter nuclei (both lighter elements eg Kr 91 + Ba 143)
3) some neutrons are also released
4) the nuclei produced are often radioactive
5) this process produces energy
6) creates chain reaction
describe the role of control rods, moderator and shielding in the fission process
control rods: limit the rate of fission by absorbing excess neutrons
moderator: slows down neutrons
shielding: absorbs the ionising radiation
