For hard $X$-rays,which of the following is true?

If the attenuation coefficient of aluminum for soft $X$-rays is $1.73 \, cm^{-1}$,what percentage of $X$-rays will pass through an aluminum sheet of thickness $1.156 \, cm$?

The wavelength of $X$-rays is of the order of .......

The potential difference between the cathode and the target in a Coolidge tube is $100 \ kV$. The minimum wavelength of the $X$-rays emitted by the tube is

The $K_{\alpha}$ $X$-ray emission line of tungsten occurs at $\lambda = 0.021 \ nm$. The energy difference between $K$ and $L$ levels in this atom is about:

Find the ratio of the energy of an $X$-ray photon with a wavelength of $1 \mathring A$ to the energy of a visible light photon with a wavelength of $5000 \mathring A$.