The half life of a radioactive substance is `20` minutes . The approximate time interval `(t_(2) - t_(1))` between the time `t_(2)` when `(2)/(3)` of it had decayed and time `t_(1)` when `(1)/(3)` of it had decay is

Options

A. 14 min
B. 20 min
C. 28 min
D. 7 min

Answer

B

Explanation

`At t _(1) (2)/(3) = (1)/(2 ^(t _(1)//20))At t _(2) 1/3 = (1)/( 2 ^(t _(2)//20))`