Half-Life

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 radioactive isotope has a half-life of 10 years, how much of a 80 gram sample remains after 30 years?

Back

20 grams.

Front

How much iodine-131 remains after 24 days if the initial amount is 10 mg and its half-life is 8 days?

Back

1.25 mg.

Front

What is the remaining mass of C-14 after one half-life if you start with 100 grams?

Back

50 grams.

Front

If you start with 100.0 g of Zn-71 and its half-life is 2.4 minutes, how much is left after 7.2 minutes?

Back

12.5 g.

Front

How many atoms of uranium-238 remain after 4.5 billion years if you start with 50,000 atoms?

Back

25,000 atoms.

Front

What is the formula to 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

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

Back

It decreases exponentially as it undergoes decay.

Front

What is the significance of half-life in radioactive dating?

Back

Half-life helps determine the age of materials by measuring the remaining radioactive isotopes.

Front

How does the half-life of a substance affect its safety in medical applications?

Back

Shorter half-lives mean the substance will decay quickly, reducing long-term radiation exposure.