When an $X$-ray tube operates at a tube voltage of $50 \, kV$,the anode current is $20 \, mA$. If the efficiency of the $X$-ray production is $1 \%$,what is the heat produced per second in calories?

Atomic number of anticathode material in an $X$-ray tube is $41$. Wavelength of $K_\alpha$ $X$-ray produced in the tube is ........ $\mathring A$.

The energy of the $L$ shell is $7200$ units and the energy of the $K$ shell is $1800$ units. Therefore,the energy of the $K_\alpha$ line is equal to ...... units.

Penetrating power of $X$-rays increases with an increase in

$X$-rays of wavelength $\lambda$ are reflected from parallel planes of atoms in a crystal with spacing $d$ between two planes, as shown in the figure. If the two reflected beams interfere constructively, then the condition for maxima will be (where $n$ is the order of the interference fringe):

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