Question

a certain radioactive isotope has a half life of 7 days. if this isoptope has 16 grams how many grams will it have after the each of the following number of days? a.)7 days b.)14 days c.) 21 days d.)28 days

Answer 1

The half life formula is

$m=m_0(\frac{1}{2})^{\frac{t}{th}}$

where m0 is the amount started with, m is the amount left after a time t and th is the half life.

In our case

$\begin{gathered} m_0=16\text{ gr} \\ t_h=7\text{ days} \end{gathered}$

Hence, we obtain:

a) After 7 days

$\begin{gathered} m=(16)(\frac{1}{2})^{\frac{7}{7}} \\ m=16(\frac{1}{2}) \\ m=8\text{ gr} \end{gathered}$

b) After 14 days

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