The minimum wavelength of $X$-rays produced in a Coolidge tube operating at $40 \ kV$ is ..... $\mathring A$.

Intensity of $X-$rays depends upon the number of

$X$-rays are:

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 $\lambda_{Cu}$ is the wavelength of the $K_{\alpha}$ $X$-ray line of copper (atomic number $Z = 29$) and $\lambda_{Mo}$ is the wavelength of the $K_{\alpha}$ $X$-ray line of molybdenum (atomic number $Z = 42$),then the ratio $\frac{\lambda_{Cu}}{\lambda_{Mo}}$ is close to:

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 ............. $mm^{-1}$.