What is the difference between soft and hard $X-$rays?

The energy of a photon of characteristic $X-$ rays from a Coolidge tube comes from

If the potential difference between the anode and cathode of the $X$-ray tube is increased,then which of the following statements is correct regarding the given $X$-ray spectrum graph?

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 $..........\; keV$.

If the series limit of the Balmer series for hydrogen is $3646 \ \mathring{A}$,calculate the atomic number $(Z)$ of the element which gives an $X$-ray wavelength of the $K_{\alpha}$ line as $1.0 \ \mathring{A}$.

The wavelengths of $K_\alpha$ lines of two elements are $250 \, pm$ and $179 \, pm$, respectively. The number of elements between these two elements in the periodic table will be: