Cutoff wavelength of X-rays coming from a Coolidge tube depends on the

The cut-off wavelength is given by:


where, λmin is the cut-off wavelength, h is the Planck’s constant(6.62607004 × 10-34 m2 kg / s), c is the speed of light in vacuum, e is the charge of the electron and V is the potential difference applied at the ends of the tube
Thus, it only depends on the potential and not the target or the temperature or the distance between the target and the filament.

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