We think that radioactive material is something buried in a bunker, which contains bombs, power plants, and perhaps some strange medical equipment. But it turns out that there is a small amount of radiation in the water, our soil, bananas, granite countertops, smoke detectors, and even some camera lenses. camera lens? Decades ago, camera companies added rare elements such as thorium to glass to change optical properties in an ideal way. Insufficiency? Well, it makes the lens a bit radioactive. A post [lenslegend] Says it all.
Strange elements such as thorium, lanthanum, and zirconium are added to the glass mixture to create the high refractive index required for complex lens designs. Select high-quality glass from large glass jars, and perform strict spectrophotometric tests after stress and strain inspections, providing valuable raw glass for the final use of lens elements.
—Konica Hexanon Lens Guide, Konica Camera Company, 1972
according to [lenslegend] This practice began in Kodak in 1945. However, by the 1980s, consumer aversion to radioactive materials and worries about factory workers stopped the production of thermal camera lenses.
Thorium is the most abundant radioactive material on earth, but it will eventually become lead. However, the half-life is just over 14 billion years, so your lenses may not turn into lead in the closet.
Although thorium only releases alpha particles, in the process, it will become radium, and then finally beta particles will be released and become a different isotope of thorium, and then it will decay into several other elements until it becomes lead. When beta radiation slows down, it produces X-rays or gamma rays.
Life-saving grace, according to [lenslegend], The amount of material is small, and the radiation is also small. However, it is clear that inhalation or ingestion of radioactive glass dust may be a problem. Alpha particles cannot pass very far through your skin. But once they enter your body, they can be dangerous. This is why radioactive glass should not be used in eyepieces.
So if you want to take apart an old-fashioned lens, you might want to know this. The Geiger counter will tell you if the lens is hot. However, if you don’t have one, you can look for yellowed glass. Radioactive decay can also cause hot spots in digital cameras.
In the consumer market, radioactive lenses do not look like a thing. However, there are some military lenses, and you can imagine that in military or industrial surplus, you might find radioactive glass.
Glass may be the world’s first engineering material, but it is still very useful. Even today, there are still new glass creation techniques under development.