You start with 400 parent atoms of a particular radioactive type, which decays to give stable offspring. You wait just long enough for three half lives to pass. You should expect to have how many parent atoms remaining (on average):

The options:

A. 400.

B. 200.

C. 100.

D. 50.

E. 25.

The CORRECT ANSWER IS D.

D. 50.

Explanation:

A half-life is the time needed for a certain amount of substance to decrease to half of its actual value. The term is mostly employed in nuclear physics to show how swiftly unstable atoms go through a process, or indicate long stable atoms passing through the phase of a radioactive decay.

It's necessary to note that after:

One half-life,

It reduces from 400 parents to 200;

At the end of the secod half-life,

It reduces from 200 parents to 100;

At the close of the third half-life,

It decreases further from 100 parents to 50.

Certain experiments of radioactive decay employs more atoms, to prevent statistical fluctuations, of which our case studies pinpoints to "on average", it uses 400 instead of 400,000,000,000,000 to give us less difficulty.

50

Explanation:

If you start with 400 atoms

After one half-life: 200 atoms

After a second half-time: 100 atoms

And after a third half-time: 50 atoms

Note that this is an example of calculation since typical studies of radioactive decay use many more atoms, to avoid statistical fluctuations.