The half-life of a radioactive substance is 40 years. How long will it take to reduce to one-fourth of its original amount and what is the value of decay constant?
Correct answer: B. 80 year, 0.0173 year
- A. 40 year, 0.9173/year
- B. 80 year, 0.0173 year
- C. 90 year, 9.017/year
- D. None of these options is correct
Explanation
The radioactive substance will reduce to ¼ of its original value in 2 half lives. As, half life is 40 years so it will reduce to ¼ in 80 years. Decay constant = 0.693/half life= 0.693/40= 0.0173
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