What is Rainbows: Definition and 26 Discussions

A rainbow is a meteorological phenomenon that is caused by reflection, refraction and dispersion of light in water droplets resulting in a spectrum of light appearing in the sky. It takes the form of a multicoloured circular arc. Rainbows caused by sunlight always appear in the section of sky directly opposite the Sun.
Rainbows can be full circles. However, the observer normally sees only an arc formed by illuminated droplets above the ground, and centered on a line from the sun to the observer's eye.
In a primary rainbow, the arc shows red on the outer part and violet on the inner side. This rainbow is caused by light being refracted when entering a droplet of water, then reflected inside on the back of the droplet and refracted again when leaving it.
In a double rainbow, a second arc is seen outside the primary arc, and has the order of its colours reversed, with red on the inner side of the arc. This is caused by the light being reflected twice on the inside of the droplet before leaving it.

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  1. S

    I Is There a Connection Between Rainbows and Holograms?

    I am currently researching holograms and realized that a rainbow has many properties associated with holograms. Obviously there are some differences, but as a student of scalar diffraction theory I see important similarities. Here is my basic reasoning, but I haven't found anybody discussing the...
  2. S

    I Rainbows on Tatooine: A Binary Star System Mystery

    I know it did not rain on Tatooine and the planet does not exist. My question is would a rainbow look like on a planet in a binary star system? Assume that it does rain, the raindrops come in a broad range of sizes including some showers with fairly uniform drop size, and that there is an...
  3. L

    B Double Rainbows and the direction of their colors

    I just saw a double rainbow. On the brighter bow the color arcs were red on the left edge of the bow and shifted to blue on the right edge. On the dimmer bow the colors shifted from blue on the left edge to red on the right. Why were they separated oppositely like this?
  4. AngularMomentum

    Presentation about Roger Bacon (rainbows)

    I need to give a presentation about roger bacon (the guy who said that rainbows form at a 42 degree angle). It's hard to find information about his study of rainbows so if anyone knows something about it I'll be grateful.
  5. Likith D

    Uncovering the Mystery of VIBGYOR: The True Colors of the Rainbow Revealed!

    I got to know 'bout primary colors Even after knowing that red, green and blue can bring infinite color combination; why do we still 'violet', 'indigo', 'yellow' and 'orange' as a part of the colors of rainbow while there are also different other colors between any two of them which are not...
  6. Likith D

    Uncovering the Mystery of Curving Rainbows: Nature vs. Lab Experiments

    We get a "naturally curved" rainbow in nature but while trying to mimic a rainbow in lab, we don't see a curved one... Can't we use the same reason that happens in nature to curve our lab-rainbow
  7. anorlunda

    Insights Rainbows are not Vampires - Comments

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  8. J

    Polarized Glasses plus Windshield Tint = Rainbows

    I bought a pair of Maui Jim sunglasses. When I tried it on daytime driving.. the roads have rainbow like effect. When I opened the windows (looking at the same road), there are no rainbows. So the windshield and window dark tint (3M) can somehow produce the rainbows when seen thru a polarized...
  9. T

    Can I Reach the End of a Rainbow with a Shovel?

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  10. T

    Is a Rainbow Close to the Ground Possible? A Camera Optics Mystery

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  11. gauss44

    Why does or doesn't a rainbow form?

    When light enters some pieces of glass from the air, such as a magnifying glass or window, rainbows usually don't form. But when light enters a prism, rainbows form. Why do rainbows form in the prism, but not in the magnifying glass or window?(This is my own personal curiosity and because I...
  12. B

    Do 'Space Rainbows' Exist Outside of Planetary Atmospheres?

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  13. R

    What is the reason for the rainbows to be circular?

    a friend of mine asked me this question after i told her that the rainbows were a phenomenon made by the sun and the rain, and also told her, that the rainbow, in fact was a full circle, but it seems to be an arch because the other half of the rainbow is "underground" and so she asked me why it...
  14. Anna Blanksch

    Do rainbows have differing archs?

    The last few times I've seen a rainbow I've wondered this... Is the arch of a rainbow always the same? As in... Does the rainbow's radius ever change? Also, why are the width of the colors and the rainbow itself always the same? I was also talking about this with a few elementary school...
  15. hxtasy

    Can Atmospheric Composition Change Prism Effects?

    not knowing much of anything about light physics, is it possible to change the effects of a prism (the visible light refracted) if it were in an environment with different air composition than our normal environmental composition? or even different pressure? so instead of 14.7 psi, 21%...
  16. E

    Rainbows in Space: Astronaut Sightings?

    Are there any circumstances, with the proper positioning, where an astronaut may witness rainbows or rainbow-ish phenomena in space? Not on the surface of another planet, mind you, but in open space. Such as in the tail of a comet, or in ice bodies or clouds of ice or other materials?
  17. M

    Rainbows (Was: Regular thread)

    Why rainbow formed ?
  18. D

    Rainbows in Space: Can We See Light Refraction?

    excuse the ignorance and improper use of terms but here goes... At work we were discussing rainbows and the topic came up "can rainbows form in space". Now I am sure that the typical rainbow arc can't be formed but can we see some sort of light refraction in space to create a visible spectrum...
  19. C

    Driving Through a Rainbow: A Real Life Story

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  20. N

    Rainbows and wave-particle duality

    Correct me if I'm wrong. The wave function of a particle collapses when you observe/measure it? Because that you essentially disturb it. Right? So how is it that we see rainbows then if it's wave function collapses as we observe it? And how is it that we are able to split white light into...
  21. H

    Exploring the Mystery of Double Rainbows

    Homework Statement What causes the faint rainbow outside of the primary one, and why are its colors reversed? Homework Equations I know that rainbows form from passing through raindrops but I don't know about the second one. The Attempt at a Solution
  22. A

    Exploring the Formation of Rainbows - Measuring Refractive Index

    Homework Statement The diagrams below illustrate the formation of a rainbow. Figure 1 shows the general arrangement and Figure 2 shows the path of a ray through a raindrop with the centre of the raindrop is labelled O. Figure 1: Figure 2: a.) Where the ray enters the raindrop in...
  23. cepheid

    Rainbows and refraction of light

    Hi, I have always wondered this about the standard explanation for a rainbow. Okay, so individual water droplets refract light entering them, dispersing it, as well as changing its direction. Fine. Here's my question: why don't we see millions of little discrete spectra, one for each droplet...
  24. H

    Rainbow: Viewing Rainbows from a Lowflying Plane

    I was wondering how a rainbow would look like when sitting in a lowflying plane. I was thinking that it sould still be a bow as standing on a mountain doesn't change the shape of the rainbow either. But is that really true? hexa
  25. M

    Understanding the Magic of Rainbows: Explained for Junior High Students

    Hello, I am interested in finding out a clear explanation for how rainbows form such as would be appropriate for the junior high level. Thanks for the help.
  26. Gara

    How do prisms separate colors in rainbows?

    I know that water drops act as a prism to turn white light into the visible spectrum. What I don't understand is how come many prisms are meant to separate the colours. What I mean is the following. One prism would make red, orange, yellow, green, blue. Two prisms would not make red...
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