The wavelength of $X-$rays is of the order of

The binding energy of the innermost electron in tungsten is $40 \, keV$. The energy of the characteristic $X$-rays emitted is:

The wavelengths of $K_{\alpha}$ $X$-rays of two metals $A$ and $B$ are $\frac{4}{1875R}$ and $\frac{1}{675R}$ respectively,where $R$ is Rydberg's constant. The number of elements lying between $A$ and $B$ according to their atomic numbers is

An electron having de-Broglie wavelength $\lambda$ is incident on a target in an $X$-ray tube. The cut-off wavelength of the emitted $X$-ray is:

Moseley's law relates the frequencies of line $X$-rays with the following characteristics of the target element:

The structure of solid crystals is investigated by using