Half-Life Practice

Front

What is half-life?

Back

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

Front

If a substance has a half-life of 10 minutes, how much of the substance remains after 30 minutes?

Back

After 30 minutes, 1/8 of the original substance remains.

Front

How do you calculate the remaining mass after multiple half-lives?

Back

Remaining mass = Original mass × (1/2)^(number of half-lives).

Front

What fraction of a substance remains after 3 half-lives?

Back

1/8 of the original substance remains after 3 half-lives.

Front

If a radioisotope has a half-life of 8 days, how much of a 16 mg sample remains after 16 days?

Back

After 16 days, 4 mg of the sample remains.

Front

What is the half-life of iodine-131?

Back

The half-life of iodine-131 is 8 days.

Front

How much of a 20 mg sample of selenium-83 remains after 100 minutes if its half-life is 25 minutes?

Back

After 100 minutes, 1.25 mg of selenium-83 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 sample has a half-life of 5 years, how long will it take for a 100 mg sample to decay to 25 mg?

Back

It will take 10 years for the sample to decay to 25 mg.

Front

What happens to the mass of a radioactive substance over time?

Back

The mass of a radioactive substance decreases over time as it decays.