The wavelength of $X$-rays decreases,when

When the atomic number of the first target is $Z_1 = 64$ and the atomic number of the second target is $Z_2 = 80$,the approximate ratio of the wavelengths of the $K_{\alpha,1}$ and $K_{\alpha,2}$ radiations is .......

In an $X$-ray tube,when the accelerating voltage is increased from $10 \ kV$ to $20 \ kV$,the difference between the wavelength of the $K_\alpha$ line and the short-wavelength limit of the continuous spectrum increases by a factor of $3$. The atomic number of the target element is:

$A$ charged gold leaf electroscope has its leaves apart by a certain amount with enclosed air. When the electroscope is subjected to $X$-rays,then the leaves

For harder $X$-rays:

The ratio of the energy of the photon emitted by the $K_{\alpha}$ line to that of the $K_{\beta}$ line is