# Question #7c67b

Jun 20, 2017

The graph is not clear.
From the given graph Half-life is $18$ days.

#### Explanation:

Half-life ${T}_{1 / 2}$ is the time taken for half of the radioactive nuclei to decay.

The accompanying graph shows the rate of decrease of the count rate or % samples remaining with time.

For any particular radioisotope the % samples remaining and time will be different. However, the shape of the curve will be the same.

In order to measure the half-life from a graph

1. Read the % samples remaining for zero days.
In our graph it is 100.

2. Go down to half point where % sample remaining is 50 and draw a horizontal line meeting the curve.
Now draw a vertical line down from this point at the curve and read off the half-life where the vertical line meets the time axis.

From the given graph Half-life appears $18$ days.