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 min
B. 5 min
C. 15 min
D. `7 (1)/(2) min`

Answer

B

Explanation

(b) `N = N_0 (1 - e^(-lamda t))`
`rArr (N_0 - N)/(N_0) = e^(-lamda t)`
`:. (1)/(8) = e^(-lamda t)`
`rArr 8 = e^(lamda t)`
`rArr 3 1n 2 = lamda t`
`rArr lamda = (3 xx 0.693)/(15)`
Half-life period
`t_(1//2) = (0.693)/(3 xx 0.693) xx 15`
`t_(1//2) = 5 min`.