Half-Life Chart

Front

What is half-life?

Back

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

Front

What percentage of a substance remains after 1 half-life?

Back

50% or 1/2 of the original substance remains.

Front

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

Back

25% or 1/4 of the original substance remains.

Front

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

Back

12.5% or 1/8 of the original substance remains.

Front

What percentage of a substance remains after 4 half-lives?

Back

6.25% or 1/16 of the original substance remains.

Front

What percentage of a substance remains after 5 half-lives?

Back

3.125% or 1/32 of the original substance remains.

Front

If a substance has a half-life of 10 years, how much of a 100g sample remains after 20 years?

Back

25g remains after 20 years (2 half-lives).

Front

If a substance has a half-life of 5 years, how much of a 200g sample remains after 15 years?

Back

25g remains after 15 years (3 half-lives).

Front

What is the formula to calculate the remaining amount after n half-lives?

Back

Remaining amount = Initial amount * (1/2)^n.

Front

How do you calculate the number of half-lives that have passed?

Back

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