MHT CET Physics question
If 20 g of a radioactive substance due to radioactive decay reduces to 10 g in 4 minutes, then in what time 80 g of the same substance will reduce to 10 g? [MP PMT 1994]
Answer: (B)
Solution
The half-life is 4 min; g takes 3 half-lives min, so 8, 16 and 20 min are wrong. Hence the correct option is (b).