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

The wavelength of $L_{\alpha}$ line in $X$-ray spectrum of $_{78}Pt$ is $1.32 \ \mathring{A}$. The wavelength of $L_{\alpha}$ line in $X$-ray spectrum of another unknown element is $4.17 \ \mathring{A}$. If the screening constant for the $L_{\alpha}$ line is $7.4$,then the atomic number of the unknown element is:

The binding energy of the innermost electron in tungsten is $40 \text{ keV}$. To produce characteristic $X$-rays using a tungsten target in an $X$-ray tube,the potential difference $V$ between the cathode and the anti-cathode should be:

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

The $X-$ray beam coming from an $X-$ray tube will be:

Characteristic $X$-rays are not obtained in the spectrum of a hydrogen atom because,