$A$ metal block is exposed to beams of $X$-rays of different wavelengths. $X$-rays of which wavelength penetrate most?

For the production of characteristic $K_{\beta}$ $X$-rays,the electron transition is:

If the wavelength of the $K_\alpha$ line of Molybdenum (atomic number $Z = 42$) is $0.7078\, \mathring A$,then the wavelength of the $K_\alpha$ line of Zinc (atomic number $Z = 30$) is .......

For hard $X$-rays,which of the following is true?

The minimum wavelength of $X$-rays produced in a Coolidge tube operated at a potential difference of $40 \ kV$ is ....... $\mathring{A}$.

The $K, L$ and $M$ energy levels of platinum lie roughly at $78, 12$ and $3 \ keV$ respectively. The ratio of the wavelength of the $K_{\alpha}$ line to that of the $K_{\beta}$ line in the $X$-ray spectrum is: