{"product_id":"large-fresnel-magnifying-lens-plastic-magnifier-260-x-177mm-solar-firelighter","title":"Large Fresnel Magnifying Lens Plastic Magnifier 260 X 177mm Solar Firelighter","description":"This is one item of a 260 X 177mm (approximately 7 X 10.25 inch) rectangular plastic fresnel lens. It is slightly smaller than A4 paper. The focal length is approximately 30cm. The magnification is a theoretical 3X based on the focal length. The material is optical PVC. You can use these as a traditional magnifier but they have a variety of fun uses such as concentrating sunlight onto small photovoltaic solar cell batteries and setting fire to things like scout camp-fires in sunshine. The thickness measures 0.53mm. The material can be cut with strong scissors or a knife.\u003cbr\u003e\u003cbr\u003eIt's worth mentioning that these are not suitable for use as reversing or side-vision lenses on cars or trucks. You need a diverging lens for that, and they are usually specially made so that they also change the angle of vision off-centre.\u003cbr\u003e\u003cbr\u003eIt is best to keep them out of the sun when not in use. I have the credit card sized items on another listing in my etsy shop.\u003cbr\u003e\u003cbr\u003eI've used these mounted in a frame to project tight beams from infra-red or visible LEDs for light based experimental free space voice or RF link transmission systems, using another similar lens and a photodiode at the receiver end. With a keyswitch on the LED you could use it for morse-code signalling over a substantial distance like an Aldis lamp.","brand":"HJW Electronics","offers":[{"title":"Default Title","offer_id":58501258707328,"sku":"FRESNEL SUB A4","price":3.9,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/1007\/2136\/1280\/files\/angle_s_a96fe68c-e9ca-421e-bdb1-edd08abaf807.jpg?v=1787495488","url":"https:\/\/shop.usefulcomponents.com\/products\/large-fresnel-magnifying-lens-plastic-magnifier-260-x-177mm-solar-firelighter","provider":"HJW Electronics","version":"1.0","type":"link"}