14-billion-years-later:

How X-rays Work.

X rays hold a certain fascination in their ability to peer into the unknown and see bizarre things like snakes that have ingested light bulbs but like a lot of good things in science, X-rays were discovered entirely by accident. They’re usually attributed to Wilhelm Rontgen who noticed that a film across his lab begun to fluoresce during experiments with a Crooke’s Tube despite taking action to block radiation (in the form of a sheet of black card). It was then discovered that by moving his hand in between the Crooke’s tube and fluorescing screen he could see the bones in his hands.

The ability for X rays to penetrate flesh and render hidden things visible lies in the amount of energy contained within them. They simply cannot be absorbed by most atoms because there is not enough of an energy difference between electron orbitals, as such they pass through most molecules and atoms unhindered. However heavier elements, such as calcium, are capable of absorbing X rays and so effectively block them. The formation of X rays lies in the reverse process. To produce high energy electromagnetic radiation electrons are accelerated and fired at a metal (typically tungsten) plate. These high velocity electrons ionize the metal by bumping off one of electrons in a lower energy orbital causing a higher energy electron to fall to the lower state and emit the difference of energies in the process as an X ray photon.