Uses of radioisotopes Flashcards
1
Q
Background radiation is due to:
A
- Radioactive substances present in rock (especially granite) and soil.
- Cosmic rays from Space.
- Man-made sources include radioactive waste from industry and hospitals.
2
Q
When using a tracer to locate a leak in an underground pipe:
A
- A very small amount of 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 after this point.
3
Q
Why are gamma sources used as tracers?
A
Gamma sources are used as tracers because the radiation is able to penetrate to the surface.
4
Q
How does a smoke detector work?
A
- A smoke detector contains an isotope which emits alpha particles.
- Without smoke, the alpha particles ionise the the air to create a tiny current 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.
5
Q
Some rock types contain traces of uranium, a radioactive material.
A
- Some rocks 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.
- The proportion of lead increases as time increases. If there are equal amounts of 235U and 206Pb, the rock is 4500 million years old.
6
Q
What is carbon-14?
A
Carbon-14 is a radioactive isotope of carbon that is present in all living organisms. By measuring the amount of carbon-14 present in an archaeological find, its approximate age can be found.
7
Q
Carbon dating can only be used on objects that were once alive.
A
- When an object dies, no carbon-14 is produced.
- As the carbon-14 decays, the activity of the sample decreases.
- The ratio of current activity from living matter to the sample activity provides a reasonably accurate date.
