rainbows

[tommy666]

how is a rainbow formed? everyone says it is caused by the light fragmenting as it passes through raindrops, but that cant be the whole story. how does the fragmented light know to join up so that we see it as a rainbow? what makes the fragmented light from these thousands of drops of water all join up together in the sky? and also, when we see a colour its just light reflecting off of something into our eyes, so what is the rainbow reflecting off of? it looks as though theres actually something there, and as if the rainbow has substance, but it doesnt, so how does the light just emit from that point? why isnt it just a big splodge of different coloured light? also, why does the rainbow linger in the air after it has stopped raining? is this because of the extra moisture in the air acting the same way as the rainbow?

thanks :D

[rojash]

The first things you need to understand are that the light is not fragmented, it is refracted (bent), and that the light doesn't know anything.
White light is made up of a whole range of frequencies of visible light. We perceive these frequencies as different colours. The amount of refraction depends on the frequency, so each of the colours will be bent by a different amount relative to the other colours, consequently, you will always see the colours "sorted" into a fixed order. The rainbow is the shape it is simply because of the shape of the raindrops - it's round. Normally, of course you only see the top half of it (so to speak)

[gammaray]

The colours are always visible in the order of Red, Orange, Yellow, Green, Blue, Indigo, Violet with Infra red and UV at opposite ends of the spectrum (these being invisible to the naked eye). You can remember the colour order by memorising this simple rhyme:

Richard Of York Gave Battle In Vain

[mibn2cweus]

Sunlight enters a raindrop, is refracted and reflected by the water droplet back out at an angle based on its wavelength. the combined refraction/reflections form an arc whose extent is determined by the area of the sky with waterdroplets obtaining sunlight. It is possible to see a rainbow which forms a complete circle by spraying a mist in a direction directly away from a bright point light source. The more defined this light point source the sharper the 'rainbow' will be seen.

For more look here

[dyli795]

It's said that a rainbow viewed from a high flying aircraft appears circular, but I've often wondered might it not in fact be spherical and only the spheres outer edge observeable. A bit difficult for me to put into words but maybe someone could enlarge on this theory. Thanks a lot if so......

[mibn2cweus]

I imagine if we could see infrared, UV, etc. the rainbow would be wider.
There is a description of a rainbow inside a rainbow seen through polarized glasses here

[BoroughGal]

dyli795 - this is an interesting link to glories (the name for round rainbows seen from aircrafts):

http://www.sundog.clara.co.uk/droplets/gloab.htm

it also has an interesting section on rainbows too:

http://www.sundog.clara.co.uk/rainbows/bows.htm as well as fogbows etc.

If you're interested in anything like this, it's one of the most interesing sites I've found.

[dancecaller]

That hardly answers the question, as there's more than one drop but only one rainbow