1.Inside an X-ray machine is a negatively charged cathode and a positively charged anode which is a flat disc made of tungsten. They sit inside a glass vacuum tube. The cathode heats up and releases electrons which fly across the tube and crash into the disc. 2.The electrons emitted from the cathode start slamming into the metal atoms in the tungsten anode. 3.This excites the atoms and causes some electrons  circling the nucleus to fall out. 4.lmmediatly other electrons in a higher orbit jump across to fill the gap. 5.The electrons have a higher energy level than the ones that fell off, so.they release their excess energy in the form of an X-ray photon. 6.The X-ray photons escape through a filtered hole in the side of the machine,pass through the person being x-rayed and on to film. X-ray pictures are taken in negative form. The parts of the body that X-rays cannot easily pass though,such as bones and teeth,show up white and softer tissue,such as skin,muscle and internal organs that can easily absorb X-rays,appear dark grey.
It all began with a famous picture of a woman's hand showing her wedding ring - and the bones underneath. It was the first X-ray the world had seen and the woman was the wife of its discoverer, Wilhelm Roentgen.
The German physics professor had come across the phenomenon earlier, while experimenting with electromagnetic radiation at his Bivarian home 110 years ago this weekend.
He watched the path of rays pass from an induction coil, through a partially evacuated glass tube and on to a screen covered in fluorescent material,which was illuminated by the rays. Roentgen put out his hand by accident - and saw the image of his skeleton.
Daniel Espino,of the Engineering and Physical Sciences Research Council,said the number of lives the discovery had saved 'must be astronomical',adding:'He realised it might have huge importance.'
Stewart Emmens,curator for medical health at the Science Museum,said the medical world realised the potential of X-rays immediately. 'It gave us a window into the internal workings of the human body,' he added.
X-rays are also used to test buildings for faults and to reveal hidden works behind paintings. Roentgen was awarded the first Nobel Prize for physics in 1901.
[The Metro Sep28,2006]