The half time is the time it takes for the radioactivity of a specific isotope to fall to half its original value.
What is half-life?
In terms of radioactivity, it is the interval of time that should be needed for one half of the atomic nuclei with respect to the radioactive sample for decaying or here the time interval should be needed for the no of disintegrations per second of a radioactive
Therefore, based on the above explanation, the third option is correct.
And, the rest of the options are wrong.
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