Tracers
- A radioactive tracer is used to follow the path of a compound through a system. E.g. Leaks in underground pipes that carry water or oil can be detected by injected radioactive tracer into the flow.
- Geriger tubes on the surface can then be used to detect the leakage.
Medical and biological uses
- Immature cells and cells that are growing or dividing most rapidly are the most sensitive to radiation. This is made used of in radiation treatment of cancer.
- Often, cancer cells are growing rapidly and are therefore much more likely to be killed by a high dose of gamma radiation from cobalt-60 source than are normal cells that divide less frequently.
Archaeological dating
- The atmosphere contains a small proportion of radioactive carbon-14 which is absorbed by living plants and trees as a result of photosynthesis.
- The half-life of carbon-14 is 5568 years so there is negligible disintegration over the life time of most plants.
- However, once the plant has died, no further carbon-14 is taken in so the proportion of carbon-14 in the plant starts to decrease as the radioactive carbon decays.
- After one half-life of 5568 years, the proportion of carbon-14 remaining is down to 50% of its initial value.
- Since activity is proportional to the number of carbon-14 atoms remaining, measuring the activity enables the age (time since death) of the dead sample to be calculated.
- To do this, the measured activity is compared with the activity of the same mass of living wood. Then using the value of half-life of carbon-14, the age can be determined.
