• Question: How are rainbows made 🌈 ?

    Asked by anon-252450 on 30 Apr 2020.
    • Photo: Susan Cartwright

      Susan Cartwright answered on 30 Apr 2020:

      Rainbows are produced when sunlight is reflected through a droplet of water – a raindrop, a droplet in a cloud, or spray from a waterfall. The physics is the same as plitting white light into colours using a prism: because the amount by which the light is bent depends on its wavelength, different wavelengths wind up iin different places. There is a good diagram at https://en.wikipedia.org/wiki/Rainbow#/media/File:Rainbow1.svg.

    • Photo: Kerrianne Harrington

      Kerrianne Harrington answered on 30 Apr 2020:

      Rainbows are light from the sun being split up through rain, because rain is transparent but also makes light travel differently than in air when it passes through it. This is a different effect for each colour. With light, when you mix all the colours of together, you get white. So light from the sun seems white, but actually has the presence of all the visible colours (and more). The droplets of water makes light split into different angles depending on it’s colour. You then see the separate colours as a rainbow :D!

      Have you ever seen a rainbow caused by moonlight?

    • Photo: anon

      anon answered on 30 Apr 2020:

      Reflections! Have you noticed that things reflected in multiple mirrors get rainbow edges? That’s exactly what happens, except in water droplets. The optics of this is very cool and rather complicated, because sunlight reflects several times inside each droplet.
      The split into rainbow colours happens because as sunlight enters the droplet, the different wavelengths (colours) get deflected (refracted) at different angles, and after all the reflections they exit the droplet in different places – so they can’t combine back to white light.
      This is also how prisms work.
      The complexity of the optics is what produces several rainbows – there is usually two (one with colours reversed), with a dark band in-between them where there is no reflected light, and if you are lucky you can see a few more – although much weaker.

    • Photo: Marios Kalomenopoulos

      Marios Kalomenopoulos answered on 30 Apr 2020:

      As others said, the main effects taking place are: reflection & refraction.
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      A nice picture that illustrates the process:
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    • Photo: Ry Cutter

      Ry Cutter answered on 1 May 2020:

      All of the answers above have already answered the question, so I’ll add some fun facts!
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      Did you know, that a rainbow is actually a circle, we can’t see the full circle unless we’re in a plane though because the Earth’s surface gets in the way.
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      The moon can also make a rainbow, we call them moonbows, they’re rather cool to look at!
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      Rainbows are wider to some animals that can see more wavelengths than us! The refracted light goes into the infrared on the red side and ultraviolet on the other. Because we can’t see these colours, the rainbow looks to have the standard 7 colours.
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      Double rainbows are part of the same rainbow! Double rainbows are formed when sunlight is reflected twice within a raindrop. This reverses the colour scheme of the second rainbow. Instead of [R,O,Y,G,B,V,I] you’ll get [I,V,B,G,Y,O,R]!
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      Great Question,
      Ry

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