What determines the hardness of the $X-$rays obtained from the Coolidge tube?

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 potential difference applied to an $X$-ray tube is increased. As a result,in the emitted radiation

The energy of the $K_\alpha$ $X$-ray line of an element is $8578$ units,and the energy of the $L$ level is $-2859$ units. The energy of the $K$ level is . . . . . . units.

The wavelength of $L_{\alpha}$ line in $X$-ray spectrum of $_{78}Pt$ is $1.32 \ \mathring{A}$. The wavelength of $L_{\alpha}$ line in $X$-ray spectrum of another unknown element is $4.17 \ \mathring{A}$. If the screening constant for the $L_{\alpha}$ line is $7.4$,then the atomic number of the unknown element is:

If the energy of an electron in the $K$-shell is $40000 \,eV$ and an accelerating potential of $60000 \,eV$ is applied across a Coolidge tube,which of the following $X$-rays will be obtained?