A radioactive sample is undergoing $\alpha$ decay. At any time $t_{1}$, its activity is $A$ and another time $t _{2}$, the activity is $\frac{ A }{5}$. What is the average life time for the sample?
A radioactive sample is undergoing $\alpha$ decay. At any time $t_{1}$, its activity is $A$ and another time $t _{2}$, the activity is $\frac{ A }{5}$. What is the average life time for the sample?
- [JEE MAIN 2021]
- A
$\frac{\ell n 5}{ t _{2}- t _{1}}$
- B
$\frac{ t _{1}- t _{2}}{\ell n 5}$
- C
$\frac{ t _{2}- t _{1}}{\ell n 5}$
- D
$\frac{\ell n \left( t _{2}+ t _{1}\right)}{2}$
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