What type of X-rays were observed?
In Röntgen’s experiments the X-rays were produced by the cathode rays striking the walls of the discharge tube (Better results may be obtained by allowing the cathode rays to impinge on a piece of metal, called an anticathode, placed in their path; the X-rays are then emitted from the anti-cathode). In general, any stream of fast moving, i.e. high energy, electrons – no matter how they are formed will produce X-rays when they lose energy and are slowed down upon striking a suitable material. This is due to the emission of radiation due to acceleration or deceleration in the atomic fields – also called bremsstrahlung (German for braking radiation – as if applying brakes to electrons and suddenly slowing them down!). As a rule, the wave lengths of the radiations emitted from an anticathode cover a considerable range, but if the X-rays are allowed to fall on a given material, most are absorbed leaving only radiations with wave lengths characteristic of the elements present in the material
