question_answer 7)

A radioactive isotope has a half-life of T years. After how much time is its activity reduced to 3-125% of its original activity (b) 1% of original value ?  

Answer:

Activity But                           ?(1) Now   A = 3.125 % of From eqn. (1), oror  t = 5T years. Similarly 1% of original value will take t = 5T years.