WAEC - Physics (1993 - No. 55)

A radioactive substance has a half-life of 20 hours. What fraction of the original radioactive nuclide will remain after 80 hours?

1/32

\(\frac{1}{16}\)

\(\frac{1}{8}\)

\(\frac{1}{4}\)

\(\frac{1}{2}\)

Fraction remaining = (\(\frac{1}{2}\))\(^{\frac{t}{T_{\frac{1}{2}}}}\)

BUT \(\frac{t}{T_{\frac{1}{2}}}\) = \(\frac{80}{20}\) = 4

Fraction remaining = (\(\frac{1}{2})^4\) = \(\frac{1}{16}\)