And if so, how far out the spectrum do they go?
I seem to recall that ultraviolet was discovered by noticing that a thermometer just above the purple band of a spectrum from a prism registered a temperature increase. Since a rainbow is formed by the same principles that cause a prism to create a spectrum pattern, I’d imagine that infrared and ultraviolet light follow the same pattern. Radiation with wavelengths over half the diameter of a raindrop (or less) would not be reflected by them however, so it wouldn’t extend to microwaves and radio waves.
Just to be very nitpicky, it was infrared that was discovered in this way (by William Herschel).
Rainbows do indeed contain infrared (IR) wavelengths. There’s a picture of an infrared rainbow (taken with IR sensitive film) in a back issue of Science or Nature – the reference is in the back of Jearl D. Walker’s book “The Flying Circus of Physics”. I’ve seen it – it looks like a regular rainbow, photographed with black and white film. Someone should re-do this with False Color and an IR camera.
As for ultraviolet (UV), I suspect that the water absorbs the UV wavelengths, preventing a UV rainbow. Most transparent substances (water, glass, plastic) block light with wavelengths shorter than 300 nm (3000 Angstroms). (I’ve never understood the big deal about UV-blocking sunglasses. They ALL block the UV.)If you want to see a UV rainbow, make it by spraying up a mist of droplets that transmit UV – like fluorocarbon fluid. Liquid Teflon ought to make a great UV rainbow.
Incidentally, you can get “rainbows” from other scattering phenomena. H. M. Nussenzveig showed that you have particle rainbows in scatter from atomic nuclei in an article on rainbows in Scientific American about 25 years ago.
FWIW, there’s not a whole lot of IR or UV in an ordinary rainbow because there’s not a lot of IR or UV in sunlight. By happy circumstance (or evolution, or deliberate creation – you pick) our eyes are most sensitive to the portion of the spectrum where the sun gives out the most energy.
Further off topic, I’ve always found it curious that Superman uses x-ray vision to see through walls and such. Since there are no x-rays in our normal environment I can see them about as well as he can and I’ve yet to see through a wall without the aid of a window. Ditto for his “heat vision”. I can buy an IR eyepiece at Costco for 200 bucks and see thermal radiation, but if I turn it around and look the wrong way through I still can’t melt steel or start anything on fire. I think Aristotle was the last person on earth who thought we see by emitting radiation from our eyes.
And then there’s that whole flying thing.
On Superman and Flying, see chapter 1 of my book “Medusa: Solving the Mystery of the Gorgon” (I kid you not: http://www.MedusaMystery.com )
Several years ago an x-ray astronomer titled a lecture “Seeing the Universe with Superman’s Eyes”.
(emphasis mine)
Yeah, but Superman isn’t one of “us”, and isn’t from Earth. Maybe Kryptonians do, in fact, see (at least in the x-ray range) by radiation emitted from the eyes. In fact, I’m pretty sure that in the comic books (sorry, graphic novels), where they go into more detail on such matters, they say exactly that-- Weren’t his heat rays originally described as being a consequence of that same radiation? Diffuse, they illuminate a surface with penetrating radiation without doing (much) damage, but focused, they burn stuff?
OK – now I’m home and can check my references. Her they are:
“Infrared Rainbow” by R.G. Greenler (I think he’s the uthor of the rainbow book) in Science, Vol. 173, p. 1231 (1971)
“Infra-Red Rainbow” by P.M. Sanders in Weather, Vol. 13, p. 352 (1958)
Cal- some plastics, which are occ used to make sunglass lenses- do not block UV very well.
Danieletc.:
Please tell me which ones. I’ve done a LOT of spectra of plastics, and virtually every one cuts off at or above 3500 Angstroms (30 nm), well above what most people would call UV. There are some plastics that transmit below this (PolyChlorotrifluoroethylene, for one), but I can’t see a sunglass manufacturer using such a weird plastic for a cheap pair of glasses. Your normal commrcial plastics don’t do a good job of transmitting the UV.
[hijack]For what it’s worth, the “new” (post-Infinity Crisis) Superman’s powers have been updated. His various “vision” powers are now taken to be a form of clairvoyance, rather than depending on real x-rays, or whatever. [/hijack]
Um, Cal, was that what you meant to say? 3500 Å is 350 nm, not 30, and UV is 400 nm and below, so either way, that’s ultraviolet.
Two points:
#1) In the surprisingly good (non-graphic)novel Superman: Last Son of Krypton, the writer Elliot S! Maggin notes that Kryptonian eyes do have the ability to emit stuff.
#2) In the late '40s and early '50s when Superman really started getting this sort of power, he used his X-Ray vision as a X-Ray laser. Heat vision hadn’t been invented yet so he’d regularly burn through stuff with x-ray vision.
By the way, Lumpy the whole “it’s all psychic…that’ll make it scientific” explaination has been utterly ignored (Yay!) since Byrne left the book. I can’t remember the last time Superman gave the standard Byrne speech about “I’m not really bulletproof, I just have a molecule thick psychic force-field./I’m not super-strong, it’s all just telekenisis.” Apparently Byrne was the only one who liked this idea (he came up with it) and the minute he left, things reverted to the pre-Crisis explanation that his powers come from the Yellow Sun and Earth’s lower gravity.
Fenris
Chronos:
The “5” in “350” didn’t register when UI hit it.Obviously, I didn’t mean 30 nm = 3500 A. (Virtually all of my spelling errors are really letters that I didn’t strike quite hard enough). Exactly where the UV starts depends on whose definition you use. Some folks take visible down into the 300s. In any case, virtually any commercial plastic is going to block anything below 3500 A, and usually quite a bit above it as well. Unless people are really concerned about 3500-4000 A, I don’t understand the big deal about “insufficient UV Blocking” in sunglasses. I don’t recall the definitions of UV A and UV B, but the wavelengths of cfoncern for most damage are shorter than 3500 A.