Answer
The wavelengths of the $K_{\alpha}$ and $K_{\beta}$ lines remain the same.
Work Step by Step
The $K_{\alpha}$ spectral line originates when an electron from the $L$ shell fills a hole in the $K$ shell. Therefore, the wavelength of $K_{\alpha}$ spectral line depends on the energy difference between $K$ and $L$ shells. Similarly, the $K_{\beta}$ spectral line originates when an electron from the $M$ shell fills a hole in the $K$ shell. Therefore, the wavelength of $K_{\beta}$ spectral line depends on the energy difference between $K$ and $M$ shells. For a fixed target, the energies of $K$, $L$ and $M$ shells are fixed. Thus, the wavelengths of $K_{\alpha}$ and $K_{\beta}$ spectral lines are fixed for each target element. Therefore, If the accelerating potential is increased from $35\;keV$ to $50\;keV$ for a molybdenum target, the wavelengths of the $K_{\alpha}$ and $K_{\beta}$ lines remain the same.
