Burn holes using an invisible sunlit rainbow

HoleBurn While messing around with ideas for my talk at the Cheltenham Science Festival, I hit on the idea of combining a piece of acrylic that only passes infrared light, with a cheap Fresnel magnifying lens. Completely by accident, I managed to get the rather pretty effect to the right. You can see that the paper is burning where there is no visible light, in the infrared portion of the spectrum. Even better, it’s quite a cheap effect to achieve.

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