Few discoveries have influenced medicine, technology and science as much as X-rays. On 8th November 1895, the German physicist Wilhelm Conrad Röntgen accidentally discovered them when experimenting with cathode rays. He first called them X-rays because of their unknown physical properties. But then he made a sensational discovery: the rays are electromagnetic, like light or radio waves. They can also be reflected or broken. They differ from light rays, however, in that they are very high-energy, making them able to penetrate solid material.

In November 1895, Röntgen presented the first X-ray photographs at a lecture on X-rays: they showed the bones of a hand – and caused a sensation worldwide. The excitement was so great that X-ray equipment was, for instance, set up in shoe shops so that customers could examine their feet through their new footwear.

The harmful effect of X-rays was not recognised until long after their discovery. A lot of people died from the radiation or became ill with leukaemia. Gradually, people began protecting themselves from the rays.

X-rays can be generated by causing currents of electrons to collide under special conditions. A negatively charged hot cathode emits electrons into an evacuated tube. They are accelerated in an electric field and collide into the positively charged anode. This creates the X-rays which can be seen on photographic material or a fluorescent screen.

An X-ray tube and a luminescent screen are the two most important components in X-ray diagnostic equipment. The object under examination is placed between the source of the rays and the screen. The denser the material, the more radiation is absorbed. The image of the object which appears on the screen (a bone for instance) is light. The exact opposite occurs with more penetrable materials such as skin or muscles.

X-ray diagnosis can help to detect fractures, bone cancer or osteoporosis, an illness which breaks down bone tissue.