Answer : The correct option is, (3) remains the same.
Explanation:
Half life : It is defined as the amount of time taken by a radioactive material to decay to half of its original value.
All radioactive decays follow first order kinetics.
The relation between the half-life and rate constant is:
\(k=\frac{0.693}{t_{1/2}}\)
The half-life of the radioactive isotope is remains the same that means a constant value and it is not affected by any external conditions.
Thus, the half-life remains the same as a sample of the radioactive isotope decays.
