Who invented $X-$rays?

Solid targets of different elements are bombarded by highly energetic electron beams. The frequency $(f)$ of the characteristic $X-$rays emitted from different targets varies with atomic number $Z$ as

Why is a direct $X$-ray photograph of the intestines not taken by a radiologist?

The $X$-rays produced by a Coolidge tube consist of . . . . .

Characteristic $X$-rays:

In tungsten,the energy of a $K$-shell electron is $20 \, keV$ and that of an $L$-shell electron is $2 \, keV$. When an electron jumps from the $L$ shell to the $K$ shell,the wavelength of the emitted $X$-ray photon will be: