Here is me at my solar furnace 
Fresnel lens FTW!
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So you built your own laser? (Great job!)
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It melts stone so… 
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I knew a kid who had one similar to that, that he could flip the lens around to “turn it on / off”…
He would put syrup in a plate, place it more or less where the focal spot would be in a while, and then wait a few hours for the ants to come marching 2 by 2 (hoorah…hoorah!!), before…well, you know…
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This fresnel lens does have a correct/incorrect position. When I I was in HS it was in edmunds scientific as 2000F solar furnace. 
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One time I decided to move my preschool classroom outdoors. Brought out the library, block area, table “toys,” and science shelf. It was a beautiful day. The sun was shining. A lovely odor of burning wood was wafting through the air.
The magnifier on our science shelf was on a stand that put it at the perfect height to magnify stuff placed underneath. Also the perfect height for that lovely sun to scorch the top of one of our expensive shelving units with its focused rays.
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My HS physics teacher made a plywood box with a 2’ circular hole, stretched mylar film across it, and sealed it. A 12V auto vacuum cleaner pulled just enough suction to form a perfect sun-catching parabolic mirror. Much burnination ensued… 
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It’s defense against the giant ants.
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When I worked for YMCA After School here in TX to pay for college, I broke up a gang of 3rd graders outside. They were playing "Who can hold their hand under the magnifying glass the longest?"
Luckily no one was hurt. Was sure I would lose my job that day.
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When I was younger, for my birthday, my brother gave me this huge science… Glass thing, with some rocks and plants and a beta fish. It was huge and round and I’m fairly certain he stole it from his university. It looked awesome.
Until my mom put it in a room with a big window, and it focused the sunlight to burn a huge scorch in the wall. The beta fish only survived for another day or so, and then my mom broke the glass thing trying to clean it.
So… Not a great birthday present. Don’t recommend.
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those aquaponics kits can be really cool. poor fish. for anyone else who wants one, keep in mind you should actually feed the betta, those singular plants are typically not enough.
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Parabolic or Catenary curve?
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