Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms (radioactive decay), but it may apply to any quantity which follows a set-rate decay. Read more on – Wikipedia

Video on Half-life

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Answer the following questions:

The half-life of 238 92U undergoing α-decay is 4.5 × 109 years. What is the activity of 1g sample of 238 92U ?

Tritium has a half-life of 12.5 y undergoing beta decay. What fraction of a sample of pure tritium will remain undecayed after 25 y.

A radioactive isotope has a half-life of T years. How long will it take the activity to reduce to a) 3.125%, b) 1% of its original value?

Obtain the amount of 60 27Co necessary to provide a radioactive source of 8.0 mCi strength. The half-life of 60 27Co is 5.3 years.

The half-life of 90 38Sr is 28 years. What is the disintegration rate of 15 mg of this isotope?

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