The radiation emitted by an X-ray tube has a minimum wavelength of 0.1e-10m. At what potential is the tube being operated? The radiation emitted by an X-ray tube has a minimum wavelength of 0.1e-10m. At what potential is the tube being operated? Solution X ray frequency (f) = eV/h wavelength = c/f V = hf/e V = hc/e*wavelength V = 6.62*10^-34*3*10^8/1.6*10^-19*10^-11 V = 12.4*10^4 volts.