A radioactive sample initially contains N atoms. After three half-lives the number of atoms that have disintegrated is
\(\frac{N}{8}\)
\(\frac{3N}{8}\)
\(\frac{5N}{8}\)
\(\frac{7N}{8}\)
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The no of atoms remaining after three half lives in 1/8.the question says the number that has disintegrated. So, the answer is 1-1/8=7/8. The correct option is D
Nice forum. However, while some of your questions contain typos that prevent candidates from arriving at correct answers, some of the answers you have provided are clearly wrong. Please endeavour to make corrections.
The ans. is correct. It is quite noteworthy to reason that 7N/8 equals the no. of atoms left undisintegrated.
The question asks for the mass of N that was disintegrated not the mass of N that was left.
