What do penicillin, Super Glue and X-rays have in common? Their inventors all discovered them by accident!

In 1895, German physicist Wilhelm Roentgen made an important discovery while experimenting with electron beams in a special tube. Wilhelm noticed that a fluorescent screen in his lab started glowing when the electron beam was turned on.

While Wilhelm knew fluorescent material normally glows when exposed to electromagnetic radiation, he was still surprised because heavy cardboard, which he thought would have blocked the radiation, surrounded the tube.

He began to experiment by placing different objects between the tube and the screen. No matter what he put between the two, the screen still glowed.

At one point, Wilhelm placed his hand in front of the tube. When he did this, he saw a silhouette of his bones projected onto the screen.

Not only had Wilhelm discovered X-rays, he saw firsthand (pun intended!) how they could become extremely beneficial to medicine.

X-rays are a type of light ray, much like the visible light we see every day. The difference between visible light and X-rays is the wavelength of the rays. Human eyes cannot see light with longer wavelengths, such as radio waves, or light with shorter wavelengths, such as X-rays.

X-rays can pass through nonmetallic objects, including human tissues and organs. An X-ray machine is like a giant camera that allows doctors to see what is going on inside a patient without having to do surgery.

To produce an X-ray picture, an X-ray machine produces a very concentrated beam of electrons onto a metal film. The beam travels through the air until it comes in contact with our body tissues.

Soft tissue, such as skin and organs, cannot absorb the high-energy rays, and the beam passes through them. Dense materials inside our bodies, like bones, absorb the radiation.

Much like camera film, the X-ray film develops depending on which areas were exposed to the X-rays. Black areas on an X-ray represent areas where the X-rays have passed through soft tissues. White areas show where denser tissues, such as bones, have absorbed the X-rays.


18 Join the Discussion

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  1. I once had an x-ray on my neck when my neck was sore. The good thing was there was no broken bones. I believed that might of made my neck sore was maybe not sleeping right or probably a mosquito bit me.

    • We’re sorry you had to get x-rays on your neck, Julie! We hope you felt better really quickly after you injured yourself. Thank you for sharing your personal connection to this Wonder of the Day®! :-)

    • We’re really glad, Julie! Thank you for letting us know! We care about all of our Wonder Friends and we’re happy you felt better quickly! :-)

    • Hi there Kaylie, thanks for sharing your comment with all of us here at Wonderopolis. We appreciate your thoughts, and we’re sorry to hear that you didn’t enjoy today’s Wonder. We value your comment and we sure hope you’ll come back to visit us soon! :)

  2. I have had an X-ray on my knee before. It was because a bone was popping out. But, my doctor said it was just a growth thing.

    • WOW, we’re so happy that you’re okay, Wonder Friend Sidney! It sounds like you have a great connection to our x-ray Wonder– thank you for sharing your comment with us! :)

    • Hi Jada! It can still work; however, the metal objects will appear in the X-ray, blocking important information with your body-or even revealing metal objects inside you! Dogs have been known to swallow a coin or too!Thanks for WONDERing with us! :)

  3. This is really cool! I have a dog she ate a long ————- balloon after a party. She’s lucky she threw it up ;-)

    • Yes, FiFi! It sounds like she was really lucky! We hope it didn’t get to the point where she needed an x-ray. Thanks for sharing with us today! :-)

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Have you ever wondered…

  • How does an X-ray work?
  • Who discovered the X-ray?
  • How do X-rays help doctors?

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Want to make your own X-ray? Draw yourself from the inside out with this fun activity!


Still Wondering

Would you believe X-rays could be useful in fields other than medicine? It’s true! Visit National Geographic Xpeditions to learn about how archaeologists use X-rays to study mummies.


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