Half Life Review

Front

What is a half-life?

Back

A 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

To calculate the remaining amount, use the formula: Remaining amount = Initial amount × (1/2)^(number of half-lives).

Front

If a substance has a half-life of 5 years, how much of a 100g sample remains after 15 years?

Back

After 15 years (which is 3 half-lives), 100g × (1/2)^3 = 12.5g remains.

Front

What percentage of a radioactive substance remains after 2 half-lives?

Back

25% of the original amount remains after 2 half-lives.

Front

If you start with 200 grams of a substance with a half-life of 10 years, how much will remain after 30 years?

Back

After 30 years (which is 3 half-lives), 200g × (1/2)^3 = 25g remains.

Front

What is the relationship between half-lives and the decay of radioactive isotopes?

Back

The decay of radioactive isotopes occurs at a constant rate, characterized by their half-lives, which indicates how quickly they decay.

Front

How many half-lives are required for a substance to decay to 12.5% of its original amount?

Back

It takes 3 half-lives for a substance to decay to 12.5% of its original amount.

Front

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

Back

The formula is: Number of half-lives = log(final amount/initial amount) / log(1/2).

Front

If a radioactive isotope has a half-life of 1 hour, how much of a 64g sample remains after 3 hours?

Back

After 3 hours (which is 3 half-lives), 64g × (1/2)^3 = 8g remains.

Front

What happens to the amount of a radioactive substance as time passes?

Back

The amount of a radioactive substance decreases exponentially over time as it undergoes decay.