Graph shows the variation of the number of radioactive atoms left undecayed with time. Find the time corresponding to `N=N_0//3` ?

Explanation

We know that `N=N_0e^(-lambdat)`
`(2N_0)/3 = N_0 e^(-lambdat_0) rArr e^(lambdat_0) =3/2 rArr lambdat_0=ln(3//2)`…(1)
Also, `N_0/3 =N_0 e^(-lambdat_1) rArr lambdat_1`=ln 3
`rArr t_1=1/lambda ln(3) = (t_0 ln(3))/(ln (3//2))` [From (i)]