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:

The wavelength of $X-$rays is

The essential distinction between $X$-rays and $\gamma$-rays is that:

The intensity of $X$-rays from a Coolidge tube is plotted against wavelength as shown in the figure. The minimum wavelength found is ${\lambda _c}$ and the wavelength of the ${K_\alpha }$ line is ${\lambda _k}$. As the accelerating voltage is increased:

An $X$-ray beam of wavelength $1 \ \mathring A$ is incident on a crystal with a lattice spacing of $2.8 \ \mathring A$. Find the value of the Bragg angle in degrees for the first-order diffraction.

The largest distance between the interatomic planes of a crystal is $10^{-7} \text{ cm}$. The upper limit for the wavelength of $X$-rays which can be usefully studied with this crystal is ............ $\mathring{A}$.