Hey,

We can determine the minimum wavelength of emitted x-rays, using the following formula:

λ m i n = h c / e V λmin=hc/eV

Where h is Planck’s constant, c is speed of light and eV the applied potential (for this purpose, the same as KV).

So, in your case it would be:

λ m i n = 1.23984193 / 50 = 0.0247968386 p m