1895: Wilhelm Roentgen

In 1895, he was studying the passage of electric currents through gas at low temperatures in a cathode ray tube when, on November 8th, he was studying in a dark room and found that a paper plate was flourescent was behind a thick, black carton. This happened as long as the plate was less than 2m away from the discharge tube. These would be later described as X-rays.

He experimented this phenomenon on his wife's hands, and shadows from her bones became visible. From this, he deduced that flesh was permeable to these rays. This would be known as the first "rontgenogram" ever taken.

It was found that X-ray photons are absorbed by the electrons in the atom. This causes them to bump up to higher energy states, putting the atom in a excited state.When they move back down to their original energy levels, they must release energy, in the form of light.

Today, X-rays are utilised for a range of important medical uses. From imaging bones to detecting pneumonia, we must thank Roentgen for the discovery of the the X-ray, as this method of examining the body is much more effective than slicing someone open!