How long will it take for a radioactive isotope with a decay constant of 0.15 (which means a half life of 4.6 days ) to decay to 5% of its original value?
(At = A0e^-kt)

A 3 days
B 4.6 days
C 5 days
D 10.73 days
E 19.97 days

Question

How long will it take for a radioactive isotope with a decay constant of 0.15 (which means a half life of 4.6 days ) to decay to 5% of its original value? 
(At = A0e^-kt)

A 3 days
B 4.6 days
C 5 days
D 10.73 days
E 19.97 days

sidsiddhartha · Answer

log(20)=kt
t=2.3026*log(20)*4.6/0.693=19.9