If half of a radioactive sample decays after 1 day, will the other half decay after 1 additional day? Why or why not?

1 Answer
Mar 12, 2018


No - half of the other half will decay in the next day.


We should assume that your sample is 100% radioactive isotopes. In the first day, 50% of the radioactive elements decay, and you are left with 50% radioactive elements, 50% non radioactive.

Now, at the start of the next day, those isotopes that are radioactive.....if you look only at the ones that are radioactive, then 100% of the radioactive isotopes are still radioactive. And in this next day, 100% of those radioactive isotopes will decay into 50% radioactive, 50% non radioactive.

On the next day, of the sample that is radioactive, 100% are radioactive.....and they will decay into 50% radioactive, 50% non radioactive....and so on and so on.

But each day, the total population of radioactive isotopes is decreasing by (1/2). 50% first day, 25% next day, 12.5% following day, 6.25%..and so on.