{"product_id":"fresnel-lens-a4-sheet-340mm-focal-length","title":"Fresnel Lens — A4 Sheet, 340mm Focal Length","description":"\u003cp\u003e\u003cstrong\u003eA full convex lens collapsed into a flat sheet — same focusing power, a fraction of the weight.\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eAugustin-Jean Fresnel's insight was that only the surface profile of a lens matters for focusing; the bulk glass in between is optically irrelevant. By collapsing the concentric zone structure to a flat profile, you get a lens that fits in a pocket. A 340mm focal length means an A4 sheet brings parallel sunlight to a point 34cm away. Applications: solar concentration, overhead projectors, fire-starting (with proper safety), magnification of large flat objects, reading aid, understanding lens equations at large scale.\u003c\/p\u003e\u003cul\u003e\n\u003cli\u003eSize: A4 (21×29.7cm) | Focal length: 340mm\u003c\/li\u003e\n\u003cli\u003ePMMA optical acrylic | 0.4mm thickness\u003c\/li\u003e\n\u003cli\u003eGroove pitch: 0.5mm | Transmission: ~90%\u003c\/li\u003e\n\u003cli\u003eIncludes sun concentration safety warning card\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003e\u003cem\u003eEvery purchase directly funds independent physics research at the Golden Physics Project.\u003c\/em\u003e\u003c\/p\u003e","brand":"Golden Physics Project","offers":[{"title":"Default Title","offer_id":54143278252324,"sku":"GPP-FRESNEL-LENS","price":19.99,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/1007\/2879\/9524\/files\/photo-1516035069371-29a1b244cc32_2d9f136b-d71d-48c2-a545-b3f678bf7976.jpg?v=1780367294","url":"https:\/\/shop.goldenphysics.org\/products\/fresnel-lens-a4-sheet-340mm-focal-length","provider":"Golden Physics Project","version":"1.0","type":"link"}