Question

. The activity of a source was measured as follows

Time/days 0 2 3 4 5

Activity 137 63 44 31 22

The background count was 7

i. Explain background count. How does it occur?

ii. Sketch the above graph and determine the half life of the source.

Answer 1

$A=A_02^{-\frac tT,}$

$T=\frac t{\log_2\frac{A_0}A}=1.83^d.$