Question

If the original number of atoms of a radioactive substance of half-life period

5 years is N, the number of atoms left after 15 years will be?

Answer 1

Answer:

1/8

Explanation:

Total time (T)= 15 years  (Given)

Half Life(T½)= 5 years  (Given)

Number of half-lives that would elapse in 15 years (n) = 15÷5= 3

Fraction of radioactive material left in the sample after the passage of 15 years equal to 3 half-lives = (1/2)³

Thus, according to formula,

=N/Nó=(1/2)ⁿ

=N/Nó=(1/2)³

= 1/8 th.

Hence in 15 years the 1/8th of the substance will remain.