4.4.2 atoms and nuclear radiation

what is radioactive decay?

a random process that gives out radiation to unstable atomic nuclei as it changes to become more stable

what is activity?

the rate at which a source of unstable nuclei decays

what is activity measured in?

becquerel (Bq)

what is count rate?

the number of decays recorded each second by a detector

what are the 4 types of radiation?

alpha, beta, gamma, neutron

what is an alpha particle made of?

2 protons and 2 neutrons (a helium nucleus)

what is a beta particle made of?

a high speed electron ejected from the nucleus as a neutron turns into a proton

what is a gamma ray particle made of?

electromagnetic radiation from the nucleus

what is the penetrating power of an alpha particle?

stopped by paper or a few cm of air

what is the penetrating power of a beta particle?

stopped by a few mm of aluminium or one metre of air

what is the penetrating power of gamma rays?

stopped by thick lead or concrete

what is the range in air of an alpha particle?

a couple of centimetres

what’s the range in air of a beta particle?

one metre

what’s the range of air of a gamma ray?

infinite

what’s the ionising power of an alpha particle?

strongly ionising

what’s the ionising power of a beta particle?

slightly ionising

whar’s the ionising power of a gamma ray?

weakly ionising

what’s an example of a count rate detector?

geiger-muller tube

what is used to represent radioactive decay?

nuclear equations

what is half life?

the time it takes for the number of nuclei of the isotope in a sample to halve or the time it takes for the count rate/activity from a sample containing the isotope to fall to half its initial level

how does a short half life present less of a risk?

it doesn’t remain strongly radioactive

how do you calculate the net decline?

initial number - number after X half lives divided by the initial number

what is radioactive contamination?

the unwanted presence of materials containing radioactive atoms on other materials

is radioactive contamination over a long or short period of time?

long period of time

what makes a substance radioactive?

if it contains radioactive atoms that emit radiation

when does contamination occur?

when a radioactive isotope gets onto a material where it shouldn’t be, often due to a radiation leak

what is irradiation?

the process of exposing an object to nuclear radiation, the irridated object doesn’t become radioactive

what method can irridation be used for?

sterilisation