Who invented $X-$rays?

If the potential difference applied across an $X$-ray tube is $V$ volts,then the approximate minimum wavelength of the emitted $X$-rays will be:

$A$ metal block is exposed to beams of $X$-rays of different wavelengths. $X$-rays of which wavelength penetrate most?

$X$-rays,when incident on a metal,do which of the following?

$\Delta \lambda$ is the difference between the wavelength of the $K_\alpha$ line and the minimum wavelength of the continuous $X$-ray spectrum when the $X$-ray tube is operated at a voltage $V$. If the operating voltage is changed to $V / 3$,then the above difference is $\Delta \lambda^{\prime}$. Then:

In vacuum,an electron of energy $10 \ keV$ hits a tungsten target. The emitted radiation will be: