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Anne Marie Helmenstine, Ph.D.

Do Radioactive Elements Really Glow?

By February 10, 2014

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Glowing Radioactive Radium Dial (Arma95)In books and movies you can tell when an element is radioactive because it glows. Movie radiation usually is an eerie green phosphorescent glow or sometimes a bright blue or deep red. Do radioactive elements really glow like that?

The answer is both yes and no. First let's take a look a the 'no' part of the answer. Radioactive decay may produce photons, which are light, but the photons are not in the visible portion of the spectrum. So no... radioactive elements do not glow in any color you can see.

On the other hand, there are radioactive elements that impart energy to nearby phosphorescent or fluorescent materials and thus appear to glow. Radium and tritium are mixed with phosphorescent materials so that the ionizing radiation from the radioactive elements can excited the electrons in the phosphors, exciting them to a higher energy level. As the electrons return to a lower energy level, visible light is produced.

If you saw plutonium it might appear to glow red. Why? The surface of plutonium burns in the presence of oxygen in the air, like an ember of a fire.

Another example of an element that glows is radon. Radon ordinarily exists as a gas, but as it is cooled it becomes phosphorescent yellow, deepening to glowing red as it is chilled below its freezing point.

Actinium is another radioactive element that glows. Actinium is a radioactive metal that glows pale blue.

While not all radioactive elements glow, there are examples of glowing elements. The elements usually do not glow green as in movies -- that color likely comes from the common phosphor color used with radium and tritium, plus it is a color that shows up really well when it is filmed.

Glowing Radioactive Materials Photo Gallery | Do Radioactive Elements Glow in the Dark


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