What does the hardness of $X$-rays obtained from an $X$-ray tube indicate?

$\Delta \lambda$ 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:

The ratio of the energy of $X$-rays with a wavelength of $1 \ \mathring A$ to the energy of visible light with a wavelength of $5000 \ \mathring A$ is:

Consider a photon of continuous $X$-ray and a photon of characteristic $X$-ray of the same wavelength. Which of the following is different for the two photons?

Penetrating power of $X-$rays can be increased by

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: