$X$-rays of which of the following wavelengths are hardest? (in $\mathring{A}$)

$X$-rays are not used for radar purposes because:

$X$-rays are produced when ...

The $K_{\alpha}$ $X$-ray of molybdenum has a wavelength of $0.071 \, nm$. If the energy of a molybdenum atom with a $K$ electron knocked out is $27.5 \, keV$,the energy of this atom when an $L$ electron is knocked out will be $.... \, keV$. (Round off to the nearest integer) $[h = 4.14 \times 10^{-15} \, eVs, c = 3 \times 10^{8} \, ms^{-1}]$

If the potential difference $V$ applied to the Coolidge tube is doubled, then the cut-off wavelength

The wavelength of an $X$-ray photon is $0.01 \ \mathring A$. Its momentum in $kg \ m/s$ is .........