The half life of a radioactive substance is 30 days. What is the time taken to disintegrate to `3//4^(th)` of its original mass ?

Options

A. 30 days
B. 15 days
C. 60 days
D. 90 days

Answer

C

Explanation

Here, `(N_0-N)/N_0=3/4` or `N/N_0=1/4=(1/2)^2`
`therefore` No of half lives, n=2
Time taken to disintegrate = Half life x No. of half lives
= 30 x 2 =60 days