Question

If a radioactive material is decayed by 20% in a
minute. Then its half period will be
(1) 80.6 sec
(2) 1863 -
(3) 100.3 sec
14) 206 3 sec​

Answer 1

Answer:

N = N0 e^-ct

N / N0 = .8 = e^-c      where t = 1 min   (c has units of 1 / min)

ln .8 =  -c

c = .223

N / N0 = 1/2 = e^(-t* .223)

ln .5 = -.223 t

t = .693 / .223 = 3.11 min = 186.6 sec