It is observed that characteristic X-ray spectra of elements show regularity. When frequency to the power 'n' i.e. $$\nu^n$$ of X-rays emitted is plotted against atomic number Z, the following graph is obtained.

The value of 'n' is

Moseley's law relates the frequency of characteristic X-rays to atomic number Z. Moseley discovered that $$\sqrt{\nu} = a(Z - b)$$, where $$a$$ and $$b$$ are constants for a given spectral line series, $$\nu$$ is the frequency of the X-ray, and $$Z$$ is the atomic number. From $$\sqrt{\nu} = a(Z - b)$$, we see that $$\nu^{1/2}$$ is linearly related to $$Z$$. So when $$\nu^n$$ is plotted against $$Z$$ and gives a straight line, $$n = 1/2$$.

The correct answer is Option 3: $$\dfrac{1}{2}$$.