Discovery of the X-Ray

For which discovery did German physicist Wilhelm Conrad Röntgen win the first ever Nobel Prize in Physics in 1901?
And the answer: X-rays.
Photo credit: public domain. 

In 1895, Röntgen was testing if cathode rays could pass through glass when he noticed fluorescence coming from a nearby chemically coated screen. He called the rays that caused the glow X-rays because of their unknown nature.

The history of medical technology has been continually shaped by groundbreaking innovations. In 1896, Röntgen took 15 minutes to capture the world-famous first X-ray shot of his wife's hand. By 1909, the time it took to capture an X-ray was down to just milliseconds— making the contours of the heart visible for the very first time.    

In Röntgen's initial X-ray, several things were happening at once. When high- energy electrons in a cathode tube hit a metal component, they either got slowed down and released extra energy, or kicked off electrons from the atoms they hit. A consequential reshuffling, again, released energy. In both cases, the energy was emitted in a form of X-rays, which is a type of electromagnetic radiation with higher energy than visible light and lower energy than gamma rays. X-rays are powerful enough to get through many kinds of matter, and portray them as semi-transparent. Soft tissue in internal organs contains few electrons, and is less visible in an X-ray machine.

When X-rays interact with matter, they collide with electrons. Substances that are more dense (like bones, for example), have a higher number of electrons and therefore can be better observed through X-ray radiation. Soft tissue, on the other hand, is found in internal organs and contains few electrons. Thus, it is less visible in an X-ray machine.

X-rays are especially useful in medicine as they are able to create distinct pictures of organs, like bones, without harming them. Despite its relative safety, those who undergo an X-ray wear lead aprons to prevent any side effects as a result of exposure to radiation.

Learn more about the history of X-rays and their application in the medical field here.


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