The life-life of `Bi^210` is `5` days. What time is taken by `(7//8)^th` part of the sample of decay ?

Options

A. `3.4 days
B. 10 days
C. 15 days
D. 20 days

Answer

C

Explanation

( c) By using
`N = N_0((1)/(2))^(t//T)` , where `N = (1 - (7)/(8)) N_0 = (1)/(8) N_0`
So `(1)/(8) N_0 = N_0((1)/(2))^(t//T) rArr ((1)/(2))^3 = ((1)/(2))^(t//5)`
`rArr t = 15 days`.