If we have "No" number of any radioactive element then after a period of "n" half-lives the number of atoms left behind is?
Answer: (1/2)^n No
Explanation
When a radioactive element undergoes decay, the number of atoms decreases by half every half-life. So, after "n" half-lives, the number of atoms left behind is:
No × (1/2)^n
Where:
No = initial number of atoms
n = number of half-lives
This is because the decay process follows a geometric progression with a common ratio of 1/2.
So, after "n" half-lives, the number of atoms left is (1/2)^n times the initial number, which is:
(1/2)^n No
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