Physics

Problem

A radioactive nucleus A with a half life

T

, decays into a nucleus B. At

t=0

, there is no nucleus B. At sometime

t

, the ratio of the number of B to that of A is 0.3. Then,

t

is given by [Main 2017] a.

t = T \log (1.3)

t = \frac{T}{\log(1.3)}

t = T \frac{\log 2}{\log 1.3}

t = \frac{\log 1.3}{\log 2}