The wavelength of X-ray photon is given by:


Here, λ is the wavelength of light, h is the Planck’s constant (6.62607004 × 10^-34 m² kg / s), and c is the speed of light in vacuum and E” is the energy of the electron which can range from 0”to eV

And the minimum wavelength that the photon can have is
where, “eV” is the kinetic energy acquired by the electron. So, in principle, x-rays can have any wavelength greater than the cut-off wavelength.