Question

The half-life a radioacitve substance is `40` yeard. How long will it take to reduce to one fourth of its original amount and what is the value of decay constant ?
A. `40 yr,0.9173//yr`
B. `90yr,9.017//yr`
C. `80yr,0.0173//yr`
D. None of these

Answer 1

Correct Answer - C
To reduce one-fourth it takes time, `t=2(T_(1//2))=2xx40=80yr`
So, decay constant, `lamda(0.693)/(T_(1//2))=(0.963)/(40)=0.0173yr`