p7 Flashcards
how does a nuclei become stable?
gives out radiation as it changes to become more stable. It is a random process called radioactive decay
what is activity
the rate at which a source of unstable nuclei decays. measured in bequerel. Bq
describe alpha particle
two neutrons and two protons. the same as a helium nucleus. highly ionising but has low penetration - can be stopped by a sheet of paper or a few cm in air
describe beta particle
a high speed electron ejected from the nucleus as a neutron turns into a proton. it is medium ionising and medium penetrating. can be stopped by a few sheets of aluminum
describe a gamma ray
electromagnetic radiation that is highly penetrating but low ionising. can be stopped by a few cm of lead
nature of radioactive decay
random
half life of a radioactive isotope
the time it takes for the number of nuclei in an isotope to half or the time it takes for the count rate of a sample containing the isotope to fall to less than half of its initial level
what is radioactive contamination
The unwanted presence of materials containing radioactive atoms on other materials
hazard from contamination
The contaminating atoms might decay, and emit radiation, the type of radiation emitted is the decay
what is irradiation
process of exposing an object to nuclear radiation. the irradiated object does not become radioactive.
sources of background radiation
- natural resources like rocks and cosmic rays from space
- man made sources like fallout from nuclear weapons testing and nuclear accidents
what is radiation measured in
sieverts - Sv
uses of nuclear radiation in medicine
- for exploring internal organs
- control or destruction of unwanted tissue
what is nuclear fission
the splitting of a large unstable nucleus
- it absorbs a nucleus
- then splits into two smaller nuclei
- emits two or three neutrons and gamma rays
- energy is released by this
what causes explosion in nuclear weapons
uncontrolled chain reaction caused by the neutrons released by nuclear fission
