X-rays are electromagnetic waves, like light waves, but with a wavelength about 1,000 times smaller. Because of this very short wavelength, X-rays can easily penetrate low-density material, such as flesh. They are reflected or absorbed, however, by high-density material such as bone. The picture made by an X-ray machine shows the denser materials (like bones) as dark areas.

X-Ray Discovery

In 1895 German physicist Wilhelm Roentgen (1845-1923) was experimenting with a cathode ray tube. The tube produced weak rays that caused a screen to fluoresce (glow). To create a controlled environment, Rontgen placed the cathode tube in a black cardboard box that was too thick for cathode rays to penetrate. Once the cathode ray tube was turned on, however, he noticed that another screen across the room began to glow. Since this second screen was too far from the tube for cathode rays to reach, especially through a layer of cardboard, Roentgen realized that he had discovered a new type of ray.

Through experimentation Roentgen found that this new ray was able to penetrate even the thick walls of his laboratory. Roentgen delivered a paper detailing his findings on December 28,1895. In the paper he admitted that he did not know the precise nature of these new rays. He chose to name them "X-rays," since "X" is the mathematical symbol for the unknown.

Few discoveries have been accompanied by as much fanfare as the X-ray. During the 12 months following the publication of Roentgen's paper, more than 1,000 books and articles were written on the subject. The number of publications rose to more than 10,000 before 1910.

A Diagnostic Tool

The penetrating power of X-rays to reveal bone structure was immediately recognized as a new medical diagnostic tool. Not all the excitement was positive, however. Many people considered the X-ray machine's ability to look through walls and doors an end to privacy. In fact, opera houses banned the use of X-ray binoculars in order to prevent patrons from peering beneath the actresses' costumes. Nevertheless, more rational minds eventually prevailed. Roentgen was awarded the first Nobel Prize for Physics in 1901.

Practical Uses of X-rays

The first medical use of X-rays came in 1896. It was American physiologist Walter Bradford Cannon who used a fluorescent screen to follow the path of barium sulfate through an animal's digestive system. This was possible only after Thomas Alva Edison invented the X-ray fluoroscope that same year. Soon after, physicians worldwide began using X-rays on humans, usually to examine bone fractures or to search for foreign objects such as bullets.

A doctor examines x-rays. By 1970 most Americans were receiving at least one X-ray exam every year from physicians and dentists.
A doctor examines x-rays. By 1970 most Americans were receiving at least one X-ray exam every year from physicians and dentists.

By 1970 most Americans were receiving at least one X-ray exam every year from physicians and dentists. However, recent evidence has shown that overexposure to X-rays can lead to the development of leukemia. Many doctors now recommend X-ray exams only when absolutely necessary

Ironically, the harmful side effects of X-ray scanning have suggested yet another use for the procedure called radiotherapy. In this therapy, very high frequency X-rays ("hard rays") are used to destroy cancer cells. Radiotherapy is most often used in conjunction with chemotherapy (cancer medicine that is taken by mouth).

X-Rays in Everyday Life

One of the most familiar X-ray machines is the baggage scanner found at airport terminals. This low-power X-ray device is placed over a conveyor belt, where it scans passengers' luggage. The machine used in this type of scanner must operate at a very specific frequency. It must be high enough to penetrate hard-shell baggage but low enough to prevent the accidental exposure of camera film.

[See also Barium ; X-ray crystallography ; X-ray machine ]

User Contributions:

Cristie Anderson
Very helpful information about x-rays and how they have changed over the course of a century. Could possibly include procedure, and how that has changed?

Thank you!
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virginia brpmga
do you know if x-rays show inflammation of bone or tissue? thank you Virginia Bronga
what are the chief parts of on x-ray outfit, because I need some info for my business and tec class. Im only a 7th grader so please help!
very useful information for my assessment task in Senior High. thank you.
Sarah 8A
Thank you! This article has been very helpful with my research for a project. :)
This is very helpful information. Thank you. You have been very helpful for my research for a project. I appreciate it. Thanks! :)
I loved this article so much. I wish there was more on the internet like this.
what are medical x-rays used for? and are they harmful to us human
maria rua
this was really awesome for my science reaserch thank you very much
Every radiology professional must know about the history of radiography.so its an important and nice and interesting article.
Thank you so much for the wonderful information. I'm doing a research project and I wanted to know who wrote this to give them credit.
Thanks again:D
How has X-rays changed through years please tell me
Mandy Macleod
very good article and very helppful . Well done !!!

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