P4 - Uses of radioactive isotopes
- Created by: Naomi
- Created on: 21-01-13 19:56
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- Uses of radioisotopes
- Background radiation
- Background radiation is due to:
- Radioactive substances present in rocks (especially granite) and soil
- Cosmic rays from space
- Man-made sources including radioactive waste from industry and hospitals
- Most background radiation is from natural sources, but some is from human activity
- Background radiation is due to:
- Smoke detectors
- A smoke detector contains an isotope which emits aplha particles
- Alpha is used because it is very ionising and won't get out of the smoke alarm
- Without smoke, the alpha particles will ionise the air which creates a tiny circuit that can be detected by the circuit in the smoke alarm
- With smoke, the alpha particles are partially blocked, so there is less ionisation of the air. The resulting change in current is detected and the alarm sounds
- The isotope needs to have a long half life so it can last a long time without needing to be replaced
- A smoke detector contains an isotope which emits aplha particles
- Dating rocks
- Some rock types such as granite contain traces of uranium, a radioactive material
- The uranium isotopes present in the rocks go through a series of decays, eventually forming a stable isotope of lead
- By comparing the amounts of uranium and lead present in a rock sample, its approximate age can be found
- The proportion of lead increases as time increases
- After one half life half of it is unchanged, and the other half has changed into lead
- After 2 half lives 1/4 of the uranium is left and 3/4 has changed into lead
- After one half life half of it is unchanged, and the other half has changed into lead
- The proportion of lead increases as time increases
- Some rock types such as granite contain traces of uranium, a radioactive material
- Background radiation
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