In radiotherapy,$X$-rays are used to

When a beam of accelerated electrons hits a target,a continuous $X$-ray spectrum is emitted from the target. Which of the following wavelengths is absent in the $X$-ray spectrum,if the $X$-ray tube is operating at $40,000 \ V$?

$X$-rays of wavelength $0.1 \ \mathring A$ are allowed to fall on a metal and get scattered. The wavelength of the scattered radiation is $0.111 \ \mathring A$. If $h = 6.624 \times 10^{-34} \ J \cdot s$ and $m_0 = 9 \times 10^{-31} \ kg$,then the direction of the scattered photons will be:

Electrons with energy $80 \ keV$ are incident on the tungsten target of an $X$-ray tube. $K$-shell electrons of tungsten have an ionization energy of $72.5 \ keV$. The $X$-rays emitted by the tube contain only:

$A$ charged gold leaf electroscope has its leaves apart by a certain amount with enclosed air. When the electroscope is subjected to $X$-rays,then the leaves

For characteristic $X$-ray of some material,which of the following relations is correct?