For the production of $X$-rays, the target should be made of

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?

Find the $(a)$ maximum frequency,and $(b)$ minimum wavelength of $X$-rays produced by $30 \; kV$ electrons.

If the frequency of the $K_\alpha$ line of an element with $Z = 64$ is $\nu_\alpha$ and the frequency of the $K_\alpha$ line of an element with $Z = 80$ is $\nu'_\alpha$,then the ratio of their frequencies is:

The frequencies of $K_{\alpha}$,$K_{\beta}$,and $L_{\alpha}$ $X$-rays of a material are $\nu_1$,$\nu_2$,and $\nu_3$ respectively. Which of the following relations holds good?

The minimum wavelength of $X$-rays produced in a Coolidge tube operating at $40 \ kV$ is ..... $\mathring A$.