Half-Life & Risk Flashcards

All 6 cards in this deck

Why is a radioactive source with a very short half-life hazardous?

It has a very high activity, so it emits a lot of radiation per second and gives a large radiation dose in a short time.

Why is a radioactive material with a very long half-life hazardous?

Its activity decreases very slowly, so it stays radioactive and remains a hazard for a very long time (must be stored and monitored for many years).

True or false? An isotope with a long half-life is always more dangerous than one with a short half-life.

False. A long half-life means lower activity but the hazard lasts far longer; a short half-life means a much higher activity now, so the hazards differ rather than one always being greater.

True or false? Radioactive isotopes have half-lives ranging from tiny fractions of a second to billions of years.

True. Radioactive isotopes have a very wide range of half-life values.

Give two precautions used to reduce the radiation dose received when working near a radioactive source.

Increase the distance from the source (use tongs or a safety screen) and limit the exposure time; keep the source in a lead-lined box when not in use.

What are the steps to compare two half-lives given in standard form?

e.g. $8.0\times10^{-1}$ s and $6.0\times10^{2}$ s

1. Compare the powers of ten first: $10^{2}$ is bigger than $10^{-1}$
2. Only if the powers are equal, compare the numbers in front
3. So $6.0\times10^{2}$ s is the longer half-life