Question

In 8,450 seconds, the number of radioactive nuclei decreases to 1/16 of the number present initially. What is the half-life (in s) of the material

Answer 1

Answer:

2113 seconds

Explanation:

The general decay equation is given as $N = N_0e^{-\lambda t}$, then;

$\dfrac{N}{N_0} = e^{-\lambda t}$ where;

$N/N_0$ is the fraction of the radioactive substance present = 1/16

$\lambda$ is the decay constant

t is the time taken for decay to occur = 8,450s

Before we can find the half life of the material, we need to get the decay constant first.

Substituting the given values into the formula above, we will have;

$\frac{1}{16} = e^{-\lambda(8450)} \\\\Taking\ ln\ of \both \ sides\\\\ln(\frac{1}{16} ) = ln(e^{-\lambda(8450)}) \\\\\\ln (\frac{1}{16} ) = -8450 \lambda\\\\\lambda = \frac{-2.7726}{-8450}\\ \\\lambda = 0.000328$

Half life f the material is expressed as $t_{1/2} = \frac{0.693}{\lambda}$

$t_{1/2} = \frac{0.693}{0.000328}$

$t_{1/2} = 2,112.8 secs$

Hence, the half life of the material is approximately 2113 seconds