Characteristic X-ray spectrum Line spectrum The methods of producing characteristic X-rays are: In this method we use element as a target in the X-ray tube and electrons are bombarded directly on it. For each target there is a minimum potential below which the line spectra do not appear, and this critical potential difference is different for different element. In this method the primary X-rays from a hard X-ray tube allow to fall on the element. The primary X-rays must be harder than the characteristic X-rays to be produced. The peak obtained in the X-ray spectrum gives the line spectrum, which is the characteristic of the element. Moseley used the potassium ferocynaide as a crystal and photographic plate as a recording medium in place of ionisation chamber in the X-ray spectrometer. He obtained line spectrum by using 30 different targets in tubes and concludes the following: The spectrum obtained by graph has two different groups. Th...