Starting with a sample of pure `""^(66)Cu,(7)/(8)` of it decays into Zn in 15 min. The corresponding half-life is

Options

A. `10` minute
B. `15` minute
C. `5` minute
D. `7(1)/(2)`minute

Answer

C

Explanation

`N=N_(0)(1-e^(-lambdat))`
`rArr (N_(0)-N)/(N_(0))=e^(-lambdat)`
`:. (1)/(8)=e^(-lambdat)`
`rArr 8=e^(lambdat t)" "rArr 3 ln 2=lambda t " "rArr=(3xx0.693)/(15)`
`t_(1//2)=(0.693)/(3xx0.693)xx15" "t_(1//2)=5 min`