A lens or mirror (that is one continous surface) of a given focal length will form an image of the sun of a certain size. The size of that image is independent of the diameter. It is only a function of the focal length. Twice the focal length/distance., twice the size.
A small flat mirror smaller than that size is just wasted effort. A mirror twice to 3 times that size probably isnt tooooo bad given such things as imperfect construction/alignment issues/whatevers. So, somewhere in that range depending on other parameters.
For reference, about a 50 inch “focal length” gives an image of the sun about half an inch across IIRC.
Also, for a given focal length, things start getting to can burn things burn level hot when the overall diameter of the mirror “system” is 1/4 th (or F4) the focal length. Make it 1/2 (F2) and now you are into solid burn stuff territory. 1/1 or F1 and its hot momma time.
Meh. It charred the surface of the wood pretty rapidly, but didn’t seem to penetrate much. I could envision a good localized third-degree burn, but you’d instinctively jerk your hand away before doing deeper damage.
Note that laser cutting is a fairly common industrial technique, and if you’ve seen videos of it, the cutting head moves pretty fast. The beam must have an awful lot of light concentrated in a very small area to be able to cut through metal that quickly. I could envision much more serious tissue damage if you were to screw up around one of those.
Attacklass would like to point out that she is a jaded 13, and while youthful, is not perhaps best characterized as a ‘youngster’.
Actually, this would likely be next years project, we don’t have the lead time for this year for a project like this.
I was going to say that if we drop a one centimeter mirror, it costs a nickle. However,
I just found a guy who sells parabolic mirrors for this sort of thing- [del]setting fire to stuff [/del] science and solar energy. This may be a game changer.
Bwah ha ha ha, my time to rule the world has finally COME! I mean, cool, what a neat idea. I was thinking the parabolic thing might work well in the context of steam generation - the beams could converge at a point inside a column of water, for instance. If not, then lets go death ray.
She’s got another hand. Hell, maybe she can regenerate, like a starfish or a time lord. More seriously, a trip to the welding store would be required for eye protection and mitts. Maybe we can get steampunk welding glasses, just for style. I’m sure that and a top hat would go over well with the judges.
