Science Fair Project Encyclopedia
Very nice diagrams of refraction (with the red lines). Very good at explaining the phenomenon.
I think that a rainbow is visible only when the sun is at a low altitude- mornings and late afternoon/ evenings. Isn't there some specific angle for this? KRS 15:33, 1 Feb 2004 (UTC)
- I added: Hence there is no rainbow if the sun is at a higher altitude than 42°: the rainbow would be below the horizon. --Patrick 23:30, 1 Feb 2004 (UTC)
Nevertheless, it is not true, as sometimes one can look below the horizon. For example, if you are looking down from a mountain, or - as mentioned in the article! - from an aeroplane.
I've deleted the incorrect reference to glories from the aeroplane comment. Glory is a different optical phenomenon from rainbow and it is incorrect to state that a full-circle rainbow is a glory. This error needs to be removed from the page Glory_(rainbow) and I've put that on my task list, but I'm not sure how to fix the problem that the error is incorporated into the page title. Advice welcome. --Richard Jones 13:45, 20 Mar 2004 (UTC)
Added: Even more rarely is a triple rainbow seen and a few observers have reported seeing quadruple rainbows in which a dim outermost arc had a rippling and pulsating appearance. - Sounds fantanstic, but I saw this, and I was not the only one - Leonard G. 03:50, 25 Aug 2004 (UTC)
The article does a clumsy job about what is special about the 42° or the 52° angle. The picture lead me to correctly see that light can be refracted-internally.reflected-refracted.again at a large range of angles, its just that 42° is where the largest intensity of refraction occurs. The page http://www.phy.ntnu.edu.tw/java/Rainbow/rainbow.html has a much better explanation for the angle. 220.127.116.11 21:46, 30 Aug 2004 (UTC)
I'm not clear on this section: In a very few cases, a moonbow, or night-time rainbow, can be seen on strongly-moonlit nights. As human visual perception for colour in low light is poor, moonbows are perceived to be white. In Hawaii, we see moonbows all the time, and it's possible to make out many colors. So, what does the editor (or author) mean by "in a very few cases"? --Viriditas 12:00, 29 Oct 2004 (UTC)
The article states: Even more rarely is a triple rainbow seen and a few observers have reported seeing quadruple rainbows... These things are not rare in Hawaii. I've seen triple rainbows many times and a quadruple rainbow only twice. --Viriditas 12:32, 29 Oct 2004 (UTC)
- More importantly we could use a scientific explanation of how they are possible. I've seen a 3+ rainbow and know that the additional bows cannot be explained using Descartes' internal reflections in a rain drop. -- Solipsist 08:32, 24 Nov 2004 (UTC)
The main mnemonic described in the article is 'Richard of York...', given the subject am I right in thinking that this is only commonly used in the UK?
Another editor has also added 'Roy G. Biv' saying it is more common. I haven't heard this one, is it common in the US? -- Solipsist 08:43, 24 Nov 2004 (UTC)
Total internal reflection?
The article states that light is reflected from the back of the drop under total internal reflection. I find this statement rather dubious at best. A quick derivation from snell's law shows that the minimum angle for total internal reflection in water (using nw = 1.33) is 48.7 degrees. That would imply that the angle at the back of the droplet is greater than 90 degrees, which by inspection is not the case.
Since light would therefore leave the back of the drop refracted, would it not be impossible to see a rainbow between the observer and the sun, if the appropriate areas of the sky were unobscured?Kenneth Charles
Edit: I did some research. Light is indeed passed out the back of a droplet, but due to the fact that there is no distinct peak of emission from this spectra, it does not form a visible rainbow. However, the statement that light is totally internally reflected inside a raindrop is wrong and should be removed.
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