What main wavelengths are within sunlight (p.s. not a hw problem)

rasgar

I ordered these giant fesnel lenses online. They are about 2.6 by 3.3 feet, and can supposedly melt asphalt. I was just wondering what is the main wavelength that causes the energy: visible light, ultra-violet, infrared, some other that I don't know about, or all of them?

Astronuc

Visible light. The material is probably optimized for the visible region of the spectrum.

http://en.wikipedia.org/wiki/Solar_radiation
http://en.wikipedia.org/wiki/Sunlight#Life_on_Earth

rasgar

So would polished aluminum be the best for reflecting it, or would some aluminum-gold alloy be more effective in reflecting it?

rasgar

I talked to an optical engineer, and she said that the energy came from the infrared spectrum, but it doesn't seem to make much sense since its a weak wavelength.

ZapperZ

But she is right. The majority of the radiant heat from the sun is in the IR spectrum.

Zz.

rasgar

So the high temperature that the fresnel lens can generate is from infrared or visible light (i.e. which one could cause that temperature change alone)?

Gokul43201

"Generate" in what object? That's one aspect of the problem to keep in mind as well. Different materials will absorb more light from different wavelengths. Most solids have absorption peaks around the IR and visible regions. How quickly you can heat up a thing with specific wavelengths depends on what the thing is made of.

ObsessiveMathsFreak

Out of curiosity, does anyone have any examples of a material that does not heat up in the IR and visible wavelength spectrum?