Radioactive decay
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?- Created by: Nadia
- Created on: 22-12-12 14:52
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- Radioactive Decay
- Radioactive decay is an event governed by the laws of probability so it is random
- the half-life: the length of time taken for half of the atoms in the sample to decay
- constant for a particular event i.e. elementshave known half-lives
- Half-lives vary between different radioactive elements from seconds to billions of years
- A sample of isotope's activity can be plotted against time on a graph to measure the half-life.
- this graph is called a radioactive decay graph
- the unit for radioactive decay is the becquerel (Bq) which is radioactive decay per second
- Carbon-14 is a 'naturally occuring radioactive isotope of carbon'.
- it emits Beta particles and has a half-life of 5370 years
- Organic objects can be dated (up to 60,000 years old) by measuring the proportion of carbon-14 to carbon-12
- Alpha particles
- helium nuclei so therefore have a charge of +2
- can penetrate only a few cm in air but stopped by thin layer of skin
- strong positive charge + high ionising power can cause a lot of biological damage once inside you
- Beta Particles
- made of electrons so charge of -1
- can penetrate~15cm of air, several cm of flesh, few cm of aluminium/ perspex
- can cause radiation burns
- Gamma Radiation
- uncharged eltromagnetic rays
- can penetrate through material very easily and through several cm of lead
- can cause radiation burns and may be delayed effects that develop e.g. cancer/ cataracts in the eye
- characteristics of different forms of radiation mean they are useful for different purposes
- e.g. medical uses like radio-imaging and radiotherapy
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