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Thread: Interesting natural occurence I didn't know about.......

  1. #1
    Senior Member CathyA's Avatar
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    Interesting natural occurence I didn't know about.......

    My brother lives in a big RV out west. He parks his RV as far out as he can, in the RV campground and takes some pretty cool pics of the night sky, with special equipment.

    But recently he posted a picture of a double rainbow. I've seen tons of double rainbows out here........but dang, never did I know the second one's colors are in the opposite direction than the first!
    The first one, as we learned somewhere is Roy G Biv, right? Well, the second one is Vib G Yor. I tried looking up why that happens, but my brain wouldn't process it. haha
    I can't believe I'm 69 and never knew this! Is this new to some of you too?

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    Senior Member bae's Avatar
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    It's pretty cool physics/optics. Our physics teacher nailed us with a question about this on our finals in high school.

    Hint: there's an extra "bounce" going on.

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    Senior Member CathyA's Avatar
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    Hi bae. I read a little about that bounce, but couldn't understand it. Can you simplify it for me?

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    Senior Member jp1's Avatar
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    https://fox41blogs.typepad.com/wdrb_...-backward.html

    The graphic partway down explains it pretty well. Basically a regular rainbow is light going in and then out of the water drop. The backwards, second, rainbow is caused by light going in, reflecting off the drop of water to another spot in the drop of water and then coming out of the drop.

    An easy way to think of this is mirrors. If you look directly at a mirror you see reverse of yourself staring back at you. But if you have two mirrors next to each other 90 degrees angled (in a corner) and you look at your reflection at that corner you don't see a mirror image of yourself, you see an actual image as if you were another person looking directly at you. This is because what you are actually seein is your image going to one mirror, reflecting to the other mirror, and then from the second mirror reflecting back to your eye.

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    Senior Member CathyA's Avatar
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    Thanks for that link jp1. But.....my brain isn't getting it. But I'll work on it.

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    Senior Member SiouzQ.'s Avatar
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    Interesting! The other day when we were driving to Santa Fe, I saw a double rainbow and the bottom rainbow had that effect - I had no idea what it was, but it was very cool! I'll post a picture but first I have to get the photo off my phone and onto my computer, then figure out how to post it here.Double Rainbow April 2019.jpg



    It's hard to see on my old Android phone, but as we were driving I was saying to my boyfriend, look how the colors are going backwards at the bottom!

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    Senior Member Rogar's Avatar
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    Pretty neat observation that I've never noticed.

    I think I have seen a triple rainbows on rare occasion. I wonder how that works. Since the explanation of a double is a slight twist of the brain, it might be too much information.

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    Senior Member CathyA's Avatar
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    That's really cool, SiouzQ!

    Rogar.....maybe I'm making it too hard, but I guess I don't understand the light being reflected by the drops of rain. ALL the drops of rain at once?? Just certain drops at any given moment in time? I just don't get it.
    It's one of those things that's just too hard for me to grasp.

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    Senior Member jp1's Avatar
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    Quote Originally Posted by CathyA View Post
    That's really cool, SiouzQ!

    Rogar.....maybe I'm making it too hard, but I guess I don't understand the light being reflected by the drops of rain. ALL the drops of rain at once?? Just certain drops at any given moment in time? I just don't get it.
    It's one of those things that's just too hard for me to grasp.
    Yes, a rainbow is millions of drops of rain reflecting the light. Since the light is all coming from the same spot (the sun) and all the drops of rain are basically the same size and side by side, they all reflect the light in the same direction. Sort of like if you had a million tiny mirrors all laid out in a big square next to each other you'd see a reflection. If those mirrors were close enough together you'd get a complete reflection.

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    Senior Member jp1's Avatar
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    Quote Originally Posted by Rogar View Post
    Pretty neat observation that I've never noticed.

    I think I have seen a triple rainbows on rare occasion. I wonder how that works. Since the explanation of a double is a slight twist of the brain, it might be too much information.
    Apparently triple rainbows are possible but quite rare. The lineup of the sun to the raindrops would have to be just perfect to get an angle where the light does three bounces in the raindrops.

    https://earthsky.org/earth/first-eve...ruple-rainbows

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