Question

Francium-223 has a half-life of 22 minutes. A geiger counter gives a reading of 58 counts per minute (cpm) from a sample of francium-223. What will the reading be 22 minutes later?.

Answer 1

The reading of the Geiger counter after 22 minutes will be 29 cpm

How to determine the number of half-lives

Half-life (t½) = 22 mins

Time (t) = 22 mins

Number of half-lives (n) =?

n = t / t½

n = 22 / 22

n = 1

How to determine the amount remaining

Original amount (N₀) = 58 cpm

Number of half-lives (n) = 1

Amount remaining (N) =?

The reading of the Geiger counter after 22 minutes can be obtained as follow:

N = N₀ / 2ⁿ

N = 58 / 2¹

N = 58 / 2

N = 29 cpm

Step-by-step explanation: