Scientists Say: X-ray

X-rays are a type of light that doctors use to peer inside the body

a doctor holds up an X-ray image against a light to observe the image of the interior of a patient's chest

Doctors use X-rays to see different tissues inside the body. Chest X-rays, for example, can be useful for diagnosing illnesses like pneumonia.

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X-ray (noun, “EX RAY”)

X-rays are a type of electromagnetic radiation.

Electromagnetic radiation is a type of energy. It includes visible light, infrared light, radio waves and other types of energy. All these types of energy travel through space as waves. But they have different wavelengths. (A wavelength is the distance from one peak of a wave to the next.) X-rays have much shorter wavelengths than visible light. They range from about 0.1 to 10 nanometers long. That makes some X-rays shorter than the width of an atom.

X-rays can pass through solid objects. But they can pass through some objects more easily than others. It depends on the density and type of material in the object. For instance, X-rays can pass more easily through muscle and fat than bone. This makes them useful for medical imaging. A machine can send X-rays through a patient’s body to a detector on the other side. Places where the detector receives fewer X-rays reveal where bones are inside the body. That can reveal if someone has broken a bone in their arm or has a cavity in their tooth.

Machines in doctors’ offices aren’t the only things that produce X-rays. Many very hot objects in the universe give off this type of radiation, such as pulsars and exploded stars. Earth’s atmosphere shields us from such high-energy radiation. So scientists must send X-ray telescopes into space to see X-ray-bright objects across the cosmos. 

In a sentence

Accretion disks of material spiraling into black holes give off X-rays.

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Maria Temming is the Assistant Managing Editor at Science News Explores. She has bachelor's degrees in physics and English, and a master's in science writing.

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