Rainbow

Discussion in 'Chemistry' started by timojin, Sep 14, 2017.

  1. timojin Valued Senior Member

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    In what form water have to be to form rainbow ?
     
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  3. Michael 345 Valued Senior Member

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    Droplets

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  5. Kittamaru Now nearly 40 pounds lighter. Staff Member

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    Well... I mean, it can be in any liquid or even solid form, I believe... doesn't even have to be water - crystals (prisms) can do it as well.
     
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  7. Beer w/Straw Transcendental Ignorance! Valued Senior Member

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    When I was little and using a hose on a sunny day I was in awe that I could make a small rainbow with water sprinkles.
     
  8. timojin Valued Senior Member

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    I know that. How come the rainbow does not come when it is raining. There have to be a more special condition , that the droplet might diffract the the visible light , the droplet must be more in a spherical form and perhaps in an equilibrium between the gravity fall and an updraft of water particles .
     
  9. Michael 345 Valued Senior Member

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    So you ask a question of which you know the answer.

    You then proceed to add "more special conditions" which indicates to me you have a reasonable understanding of rainbow effects

    Huey Duey and Louie can only add about raining - the absence of the sun shining behind you

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  10. origin Trump is the best argument against a democracy. Valued Senior Member

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    The sun shining through rain is all it takes to make a rainbow.
     
  11. exchemist Valued Senior Member

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    Because when it is raining the sun isn't shining. Durrh.

    More seriously, you get a rainbow when the sun shines onto a part of the sky where there are transparent particles (water or ice). Most people know you see one opposite to the direction of the sun, from where you are standing. That is because the mechanism (which you can easily look up on the web) involves reflection from the inside surface of the particle, as well as frequency dispersion of the light.
     
  12. timojin Valued Senior Member

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    I am familiar with some things but I want some different views . Unfortunately most of the time you don't offer but sarcastic criticism.
     
  13. timojin Valued Senior Member

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    Question is is it inside of the particle or is it refraction from the surface of the particles, does the particle have to be spherical or deformed ?
     
  14. timojin Valued Senior Member

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    Thank you for your wisdom , it happen when the rain ends the rainbow appears.
     
  15. Michael 345 Valued Senior Member

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    Oh you noticed

    Meet Mr Google and Ms Wiki

    https://en.m.wikipedia.org/wiki/Rainbow

    They should be able to answer all your questions without sarcasm

    As for myself and Huey Dewey and Louie we don't have any alternative views on reality although I have heard about the pot of gold at the end of the rainbow but I have doubts about its authenticity

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  16. origin Trump is the best argument against a democracy. Valued Senior Member

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    You think rainbows appear when it is not raining? Too bad you are ignoring my wisdom - you could have learned something. [shrug]
     
  17. billvon Valued Senior Member

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    Nope. It has to be raining. The only time you will see a rainbow is when it's raining and sun shines through the rain. (Note that the sun, and/or the rain, doesn't have to be on YOU - it just has to illuminate the rain at the right distance/angle from you.)
     
  18. timojin Valued Senior Member

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    Nope what ? If raining is in my area I will see rainbow, you are funny. First of all, if it rains there is no sunshine . If in my area the sky is open and possible sunshine and a mild rain might be in a distant area than
    I might see the rainbow. It also depends on the of the quality of rain.
     
  19. billvon Valued Senior Member

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    If all the rain ends you will not see a rainbow. If there is no sun at all you won't see a rainbow. You need rain and sun at the same place, and that place also needs to be the right angle from you relative to the sun. (Which is why rainbows are relatively rare.)
     
  20. origin Trump is the best argument against a democracy. Valued Senior Member

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    That rainbows appear after it stops raining - that is not true.
    If the sun is shinning as it rains on you there is a good chance that you will see a rainbow. Doesn't seem very funny to me.
    Really? You have never seen it rain when the sun was shining? Do you get out much?

    Here is an in depth analysis of how this amazing thing could happen. There is rain cloud above you and closer to the horizon the sun is unobstructed by clouds.
    And so ends my in depth analysis
    What does the quality of the rain mean? Do you have any evidence of this strange rainbow quality rain?

    I am mystified why this is so difficult for you. Is this just a very poor attempt at trolling?
     
  21. exchemist Valued Senior Member

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    You get refraction on entry to the side of the particle facing the sun, then reflection off the back surface of the particle, still within the particle, and then further refraction on exit from the particle, back towards the sun again, but at a different angle. You can find pictures of this process in lots of place on the web. So long as the particles are roughly spherical you get the effect.

    Picture here, since you are such a lazy git

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    : https://en.wikipedia.org/wiki/Rainbow#/media/File:Rainbow1.svg
     
  22. timojin Valued Senior Member

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    Thanks for the pictures , but I thought to revive in my mind the forum on water particle a while ago that not all water particles are the same . and to have a rainbow the particles have to be spherical.
     
  23. Michael 345 Valued Senior Member

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    This is non spherical water helping oil make rainbows

    Why do beautiful bands of color appear in the tiny oil slicks that form atop puddles on a rainy day? More specifically, why does each band have a different color, and why do the various bands remain distinct?

    The following answer comes from Dinesh O. Shah; he is Charles A. Stokes Professor of Chemical Engineering and Anesthesiology at the University of Florida at Gainesville:
    "When you see an oil film on the road on a rainy day, it gives rise to bands of beautiful colors for the following reason:

    "Small amounts of oil are usually present on the road surface (for instance, lubricating oil from cars, trucks and bicycles). When it rains, drops of oil float on the layer of water that collects on the road because the density of oil is less than that of the water--the same reason that wood floats on water. Commercial oil formulations usually contain a surfactant, an additive that causes the oil drops to spread out into a thin film atop the water. That film is thickest in the center of the patch, or oil slick, and thinnest at the periphery.

    "Light reflects upward both from the top of the oil film and from the underlying interface between the oil and the water; the path length (the distance from the reflection to your eye) is slightly different depending on whether the returned light comes from the top or from the bottom of the oil film. If the difference in path length is an integral multiple of the wavelength of the light, rays reflected from the two locations will reinforce each other, a process called constructive interference. If, however, the rays reach your eye out of step, they will cancel each other out due to destructive interference.

    Sunlight contains all the colors of the rainbow--the famous ROYGBIV (red, orange, yellow, green, blue, indigo, violet). Each color of light has a different wavelength. Hence, a given disparity in the path length will cause constructive interference of certain colors, whereas other colors will not be observed because of destructive interference. Because the oil film gradually thins from its center to its periphery, different bands of the oil slick produce different colors.


    https://www.scientificamerican.com/article/why-do-beautiful-bands-of/

    Thank you Mr Google

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