The wavelength of the most energetic $X$-rays emitted when a metal target is bombarded by $40 \ keV$ electrons is approximately .............. $\mathring{A}$.

The Compton effect is associated with

For continuous $X-$rays,the minimum wavelength produced is:

An $X$-ray tube with a copper target emits a $Cu$ $K_{\alpha}$ line of wavelength $1.50 \ \mathring{A}$. What should be the minimum voltage through which electrons are to be accelerated to produce this wavelength of $X$-rays? $(h = 6.63 \times 10^{-34} \ \text{J}\cdot\text{s}, c = 3 \times 10^8 \ \text{m/s})$

If the potential difference $V$ applied to the Coolidge tube is doubled, then the cut-off wavelength

The patient is asked to drink $BaSO_4$ for examining the stomach by $X$-rays because $X$-rays are