Radioactive substances present in rocks (especially granite) and soil, cosmic rays from space, man-made sources including radioactivr waste from industry and hospitals.
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Where is most background radiation from?
Natural sources but some comes from human activity
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What are tracers used for?
To locate leaks in underground pipes
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What happens during using a tracer?
A very small amount of a gamma emitter is put into the pipe, a detector is passed along the ground above the path of the pipe, an increase in activity is detected in the region of the leak and little or no activity is detected in other points
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What does a smoke detector contain?
An isotope which emits alpha particles
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What happens in a smoke detector without smoke?
The alpha particles isonise the air which creates a tiny current that can be detected by the circuit in the smoke alarm
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What happens in a smoke detector with smoke?
The alpha particles are partially blocked so there is less ionisation o the air. The resulting change in current is detected by the circuit in the smoke alarm
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What do some rock types contain?
A radioactive material called uranium
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What happens to the uranium isotopes in the rock?
It goes through a series of decays, eventually forming a stable isotope of lead
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How can the approximate age be found?
By comparing the amounts of uranium and lead present in a rock sample
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What is carbon-14?
A radioactive isotope of carbon that is present in all living things.
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When can carbon dating be used?
On objects that were once alive
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What happens when the object dies?
No more carbon-14 is produced, as the carbon 14 decays, the activity of the sample decreases, The ratio of the current activity from living matter to the sample activity provides a reasonably accurate data
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Other cards in this set
Card 2
Front
Where is most background radiation from?
Back
Natural sources but some comes from human activity
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