Assertion. Average life of a radioactive element is that period in which `63%` of it is decayed.
Reason. Average life `tau=1.44" t"_(1//2).`

Options

A. If both assertion and reason are true and the reason is the correct explanation of the assertion.
B. If both assertion and reason are true but reason is not the correct explanation of the assertion.
C. If assertion is true but reason is false.
D. If the assertion and reason both are false.

Answer

A

Explanation

`t=(2.303)/(k)log"(a)/(a-x)`
`k=0.693//t_(1//2)`, `a=100`, x=63
`tau=(2.303)/(0.693//t_(1//2))log"(100)/(100-63)`
`tau=1.44t_(1//2)`
So reason is the correct explanation for assertion.