How do the colors of the rainbow work

[peter.ell]

I know this may sound like a stupid question, but after reading about and even watching an entire MIT lecture on rainbow formation, I just don't understand how the colors of a rainbow can show up separately.

Given what I learned about the light paths for different colors in a rainbow, I know that red light is not only refracted at the angle where red is seen in a rainbow, but also at all the other angles. Given this, it means that, while green light is not refracted at the top of a rainbow where red is, red happens to be refracted where green is... which should mean that we would not be able to see any of the colors in a rainbow except for red and whatever the combination of red and all the other colors turns out to be. Yet we don't, why not?

As a side note, the fact that at each color in refracted at angles other the minimum angle of deviation is why the sky seems brighter inside of a rainbow--all the colors just happen to be overlapping and thus white light is produced.

Thanks for helping me out!

 

[mathman]

The main point is that the different colors are refracted at different angles, so they separate.

 

[Drakkith]

Red light is refracted at a certain angle, which means that all of the red light gets reflected at that angle and none at the green angle because there is no more red light, right? And then so one and so on for the rest of the colors.

 

[SSJVegetto]

The colors separate because every color has a different wavelength and is refracted at a different angle. The same thing a prism does is happening within a water droplet.

See:
http://en.wikipedia.org/wiki/File:Rainbow1.svg"
http://en.wikipedia.org/wiki/File:Dispersive_Prism_Illustration_by_Spigget.jpg"

 

[peter.ell]

Red light is refracted at a certain angle, which means that all of the red light gets reflected at that angle and none at the green angle because there is no more red light, right? And then so one and so on for the rest of the colors.

Actually, no. Not according to this and many other sources: http://video.google.com/videoplay?docid=-2978729867097229598#

If what you're saying is true, than there would be no white light inside of a rainbow.

 

[sophiecentaur]

Don't confuse Colours with Wavelength. White light has a spectrum of different Wavelengths. Colours are what we see and experience with our brains. They are mostly due to a whole mixture of wavelengths and may not be part of the 'spectrum' at all. These topics involve Wavelength - not colour.

A rainbow is a 'virtual image'. It's not 'really there' but appears in the sky as a set of circles around an axis which passes, from the Sun, through the back of your your head. The Sun is always behind you for this. As you move around, the 'bow' moves with you. The end of the rainbow will be undefined - depending on the extent of the rain and the height of the Sun. In a plane, you may see a whole circle or you can see it apparently right in front of you when you use a hose in the garden.

Each droplet disperses the white light so that the different wavelengths emerge in different directions. When we see a band of long wavelength (red) light, we are seeing just the red light from a particular set of drops on a cone of a particular angle - hence we see a circle of red. The other wavelengths from these particular drops are going somewhere else- so we don't see that light. We do, however, see green light from a different set of drops on a different cone with a different angle. So we see a set of bands, of different wavelengths, with the red (longest wavelength) on the inside and the violet (shortest wavelength) on the outside.
google rainbow for some very pretty diagrams.

 

[SSJVegetto]

If you really want to understand more just watch this video:
http://video.google.com/videoplay?docid=-2978729867097229598#"

 

[Drakkith]

Actually, no. Not according to this and many other sources: http://video.google.com/videoplay?docid=-2978729867097229598#

If what you're saying is true, than there would be no white light inside of a rainbow.

Forgive me if I'm wrong, but i didn't think there was white light in a rainbow.

 

[sophiecentaur]

If you really want to understand more just watch this video:
http://video.google.com/videoplay?docid=-2978729867097229598#"

Another good MIT lecture.

 

[davenn]

If you really want to understand more just watch this video:
http://video.google.com/videoplay?docid=-2978729867097229598#"

thanks for the link, I learned lots :)

Dave