Tungsten, w-181, is a radioactive isotope with a half life of 121 days. if a medical lab purchases 24 kg of w-181, how much will be left after 1 year? a) 24 kg b) 12 kg c) 6 kg d) 3 kg

The correct answer of this question is : 3 Kg

EXPLANATION :

As per the question, the half life period of W-181 :  

The initial amount of the specimen

We are asked to calculate the amount of specimen left after one year.

Hence, the total time t = one year = 365 days.

Hence, total number of half lives n =

                                                          =

                                                          =

                                                          = 3.

Let the amount left after one year is N.

Hence, the rest amount of specimen is calculated as-

                       ⇒

                                                   [ans][

v=ir = 3x15 =45 v