Half Life Calculations

Front

What is half-life?

Back

Half-life is the time required for half of the radioactive atoms in a sample to decay.

Front

How do you calculate the remaining amount of a substance after a certain number of half-lives?

Back

Remaining amount = Initial amount × (1/2)^(number of half-lives)

Front

If the half-life of a substance is 8 days, how much of a 10 mg sample remains after 16 days?

Back

2.5 mg

Front

What percentage of a substance remains after one half-life?

Back

50% of the original amount remains.

Front

What percentage of a substance remains after two half-lives?

Back

25% of the original amount remains.

Front

What is the formula to find the number of half-lives that have passed?

Back

Number of half-lives = Total time elapsed / Half-life duration.

Front

If a substance has a half-life of 10 seconds, how long will it take for it to reduce to 1/8 of its original amount?

Back

30 seconds (3 half-lives).

Front

What is the remaining percentage of a substance after three half-lives?

Back

12.5% of the original amount remains.

Front

If you start with 80 g of a substance with a half-life of 5 years, how much will remain after 15 years?

Back

10 g.

Front

What is the relationship between half-life and decay constant?

Back

Decay constant (λ) = ln(2) / half-life.