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? you can ignore background radiation.

29 counts per minute (29 cpm)

Explanation:

The half-life of a radioactive isotope is the time needed for the activity of the sample to halve.The half-life of Francium-223 is exactly 22 minutes: this means that its activity after 22 minutes becomes exactly half of its initial value. Since the initial activity of this sample of francium-223 was 58 cpm, the activity after 22 minutes will be

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

n = t /  t½

n = 22 / 22

n = 1

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

Learn more about half life:

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