Question

Which statement about the half life of a radioactive sample is true?

Answer 1

The radioactive decay can be expressed through the following exponential law:

If [A]₀ is the initial concentration of the radioactive nuclei and [A] is the concentration after a decay time t, then:-

[A]/[A]₀ = exp(-kt)

or, k = -1/t * ln[A]/[A]₀ ----(1)

where k = decay rate constant

Now, the half life is given as :

t1/2 = 0.693/k ----(2)

Thus, the half life is dependent on k which is in turn dependent on the concentrations, [A] and [A]₀

Ans: c) it is affected by the concentration of the radioactive substance that is present.

Answer 2

The correct answer is B. it measures the tendency of a radioisotope to decay radioactively.