The half-life of a radioactive substance against `alpha-`decay is `1.2 xx 10^7 s`. What is the decay rate for `4 xx 10^15` atoms of the substance ?

Options

A. `4.6 xx 10^12` atoms/s
B. `2.3 xx 10^11` atoms/s
C. `4.6 xx 10^10` atoms/s
D. `2.3 xx 10^8` atoms/s

Answer

D

Explanation

(d) `(dN)/(dt) = -lamda N rArr |(dN)/(dt)| = (0.693)/(T_(1//2)) xx N`
=`(0.693)/(1.2 xx 10^7) xx 4 xx 10^15 = 2.3 xx 10^8 `atoms/sec.