physics : 7.9, 7.10, 7.11, 7.12, 7.13

How can all types of radioactive decay be detected (G-M)

• All types of radioactive decay can be detected by a Geiger-Muller tube

• ionise the gas inside the G-M tube

• resulting charged particles move across the chamber, get counted as charges like an ammeter.

Photographic film

• turn from transparent to dark and non-transparent.

• film badges have windows of different thickness and material so shows type of radiation the worker has exposed to.

sources of natural background radiation

cosmic rays : radiation that reaches the Earth from space

rocks and soil : some rocks are radioactive and give off radioactive radon gas

living things : plants absorb radioactive materials from the soil, which is passed up the food chain

artificial sources of background radiation

x-rays : whilst having an x-ray or traveling in air

nuclear missile : bombs such as Hiroshima which have released radiation into the environment

nuclear power : nuclear power stations release radiation into the atmosphere

artificial vs natural background radiation percent

15% is from artificial sources

biggest background radiation

50% radon gas from ground

biggest artificial background radiation

medical usage

what is the amount of radiation a person receives measured in

Sieverts (SV). 1 Sv is a very big dose and would cause acute radiation poisoning, most people receive 0.003 Sv or 3mSw a year

what is radioactive activity measured in

Becquerels

what happens to a radioactive source over time

the activity decreases because each decay event reduces the overall number of radioactive particles in the source

half life

the time it takes for the number of nuclei of a sample of radioactive isotopes to decrease by half

A particular radioactive sample contains 2 million un-decayed atoms. After a year, there is only 500 000 atoms left un-decayed. What is the half-life of this material?

1) calculate how many times the number of un-decayed atoms has halved
2) divide the time period by the number of half-lives

what is ionsising radiation

radiation that knocks electrons off atoms, creating ions