What does the hardness of $X$-rays obtained from an $X$-ray tube indicate?

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?

In $X$-ray spectrum,the wavelength $\lambda$ of the $K_{\alpha}$ line depends on the atomic number $Z$ as:

The range of wavelength for $X$-rays is from . . . . . . .

When $0.50\; \mathring{A}$ $X$-rays strike a material,the photoelectrons from the $K$-shell are observed to move in a circle of radius $23\; mm$ in a magnetic field of $2 \times 10^{-2}\; T$ acting perpendicularly to the direction of emission of photoelectrons. The binding energy of $K$-shell electrons is $..........\; keV$.

When the accelerating voltage applied to the electrons is increased beyond a critical value in an $X$-ray tube,what happens to the $X$-ray spectrum?