The typical wavelength of $X$-ray is

The intensity distribution of $X$-rays from two Coolidge tubes operated on different voltages $V_1$ and $V_2$ and using different target materials of atomic numbers $Z_1$ and $Z_2$ is shown in the figure. Which one of the following inequalities is true?

How does the wavelength $\lambda$ of the $K_\alpha$ line in the $X$-ray spectrum depend on the atomic number $Z$?

Moseley's law for characteristic $X$-rays is given by $\sqrt{f} = a(Z - b)$. Choose the correct statement.

Who invented $X-$rays?

An electron beam is accelerated by a potential difference of $V$ and strikes a metal target to produce $X$-rays. For which of the following values of $V$ (in $kV$) will the $X$-ray wavelength be the shortest?