Забавное. из описания 18х26 см линзы френеля на ебае:

This Fresnel lens is also very good for experiments of gathering solar energy. Thanks for its large size, it usually can start a fire within 2 seconds in a normal sunny day. I personally can use it to start melting an aluminum can around 45 seconds under Florida sunshine. Try it your ways to boil a bottle of water, start a camp fire, or build a water heat pipe, etc. I guarantee that you have a lot fun!

#oinnni

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