If $V$ is the accelerating voltage,then the maximum frequency of continuous $X$-rays is given by

Assertion : Soft and hard $X-$ rays differ in frequency as well as velocity.
Reason : The penetrating power of hard $X-$ rays is more than the penetrating power of soft $X-$ rays.

The wavelength of the series limit of the Lyman series in the hydrogen spectrum is $911 \ \mathring{A}$. Calculate the atomic number of the element that emits characteristic $X$-rays with a minimum wavelength of $0.7 \ \mathring{A}$.

An electron having de-Broglie wavelength $\lambda$ is incident on a target in an $X$-ray tube. The cut-off wavelength of the emitted $X$-ray is:

$X$-rays are produced due to which of the following?

If $X$-rays are produced by bombarding electrons with an energy of $40 \ keV$ on a target,what will be the minimum wavelength (in $\mathring{A}$) of the $X$-rays produced?