For a certain radioisotope the natural logarithm of activity (in Bq) plotted against…

PHYSICS · Subjective · A Level · Physics · Nuclear physics · Nuclear physics

Problem

For a certain radioisotope the natural logarithm of activity

A

(in Bq) plotted against time yields a straight line whose slope is

-5.0\times10^{-4}\,\text{s}^{-1}

. (i) Find the decay constant

\lambda

of the isotope. (ii) Determine its half-life in minutes. (iii) If the initial activity is

6.0\times10^{4}\,\text{Bq}

, calculate the activity after 20 min. (iv) After how many seconds will only 5 % of the initial nuclei remain undecayed?