$X$-rays are:

The ionization energies of Cobalt $(Co)$,Copper $(Cu)$,and Molybdenum $(Mo)$ are $7.8 \, keV$,$9.0 \, keV$,and $20.1 \, keV$ respectively. If any of these metals are used as a target in an $X$-ray tube operating at $15 \, kV$,then:

When $X$-rays of wavelength $0.5 \, Å$ pass through an $Al$ sheet of thickness $10 \, mm$, their intensity is reduced to one-sixth of its initial value. The absorption coefficient for aluminum is ............. $mm^{-1}$.

Hard $X$-rays for the study of fractures in bones should have a minimum wavelength of $10^{-11} \, m$. The accelerating voltage for electrons in the $X$-ray machine should be:

An $X$-ray tube has a short wavelength limit at $0.45 \mathring{A}$. The voltage of the tube is ........ $V$.

$X-$rays are known to be electromagnetic radiations. Therefore,the $X-$ray photon has