Now I know that rainbows are formed due to refraction of light from the sun hitting raindrops and light waves leave at varying angles between 40-42 degrees or somewhere around there. Also, that they’re round.

What I don’t understand is how it’s consistent, like I assume it’s hitting many raindrops, but all these drops are in different places so why does it still form a nice circle. Furthermore, why isn’t the whole sky a rainbow if it’s raining and thus hitting all the drops. I suspect the angle of the sun is playing a part but I’m not a science man.

Please help me get this thought out of my head.

  • SwearingRobin@lemmy.world
    0·
    5 months ago

    You’re almost there. It has to do with the angle of the sun and the water drops relating to the view point. Rainbows only show when the sun is behind you, and if you imagine a cone going out from the viewpoint outwards you get the possible paths of the rainbow (different radius different wavelength and therefore color)

    A similar concept happens in certain reflective surfaces (metal pots and pans, car hoods and much more). You always see the tiny scratches in circles, but if you alter the angle in any way you keep seeing different scratch circles. This is because the circle you see in any given angle is the exactly the scratches that are turned just perfectly to reflect the light in the perfect way. It does not mean that the scratches you see at any given moment are the only ones. It means there are plenty, and only a few more visible at a time.

    To me, playing around with the second concept (much easier to manipulate yourself and see) made me understand rainbows much better.

    • dependencyinjection@discuss.tchncs.deOP
      0·
      5 months ago

      Thanks.

      I hadn’t considered the placement of the sun being behind me, but can confirm I was walking each when I saw a rainbow the other day, it was evening meaning the sun was setting in the west. So behind me.

      Also, the scratches on cars is a god damn revelation to me and something I had no idea about. I will be playing around with looking at these now so thanks for bringing that up.

      • SwearingRobin@lemmy.world
        0·
        5 months ago

        Happy to help! Now what I don’t get under this knowledge is double and triple rainbows. If anyone can explain that to me I would be very grateful.

        • dependencyinjection@discuss.tchncs.deOP
          0·
          5 months ago

          Sometimes the light reflects twice off the back of the raindrop; this leads to the secondary rainbow. The second reflection causes the order of the colors in the bow to reverse.

          This seems to be the how sourced from Here