Fresnel Lens — A4 Sheet, 340mm Focal Length

A full convex lens collapsed into a flat sheet — same focusing power, a fraction of the weight.

Augustin-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.

• Size: A4 (21×29.7cm) | Focal length: 340mm
• PMMA optical acrylic | 0.4mm thickness
• Groove pitch: 0.5mm | Transmission: ~90%
• Includes sun concentration safety warning card

Every purchase directly funds independent physics research at the Golden Physics Project.