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Credit card magnifier. Photo © Eugene Brennan
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My latest gadget from Temu, a credit card-sized magnifier. This is really useful and the scientific angle is that it makes use of a Fresnel lens. This type of lens is used in front of the lamps in lighthouses and also as the plastic window in PIR sensors. "Normal" spherical lenses are made from a curved piece of glass, plastic or quartz, making use of the refractive powers of the material to bend light. However they can be quite thick when used for high magnification. A Fresnel lens reduces the thickness and volume of material required by using individual elements or concentric, prismatic rings, so that magnifiers can even be manufactured in flat sheet.
More info about Fresnel lenses is available on Wikipedia here.
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© Eugene Brennan
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