Question

How much should be the voltage of an $X$-ray tube, so that the electrons emitted from the cathode may give an $X$-ray of wavelength $1\mathring{A}$ after striking the target?

Answer 1

Voltage of X-ray tube $=V=\frac{12400}{\lambda }\mathring{A}$
$=\frac{12400\times {10}^{-10}}{1\times {10}^{-10}}$
$=12400V$