A mixture consists of two radioactive materials A1 andA2 with half lives of 20 s and 10 s respectively. Initially the mixture has 40 g of A1 and 160 g of A2. The amount of the two in the mixture will become equal after: Option 1) 60 s Option 2) 80 s Option 3) 20 s Option 4) 40 s

For A1, N01=40g, t1/2= 20 sec

For A2, N02=160g, t1/2 = 10 sec

Let us say at t =t, amount of A and Abecome equal then at t = t

&

or

Option 1)

60 s

This option is incorrect.

Option 2)

80 s

This option is incorrect

Option 3)

20 s

Option 4)

40 s