What is Rainbow: Definition and 61 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. T

    I The Science Behind Rainbows: Explaining the Center of a Rainbow | Gooood Morning

    Gooood Morning I was traveling with my son and he noted the rainbow out the window and asked why we see only half. I informed him that the earth blocks the other half and if we were in an airplane, we could see the entire circle. Set that aside. When we look at the electromagnetic spectrum...
  2. CandiAnne

    I Calculating Material Dimensions for a Semi-Circular Window Rainbow

    Hello math wizards!!!!! I have a half circle window in my home that I'm trying to cut material for to make a rainbow. Window across is 69" All blind slats around the arc are 22.25" At the bottom of the window there is a Center Circle that is 12 tall and 25 width What length, width and arc...
  3. A

    Light refracting and reflecting in a drop of water to form a rainbow

    I drew the red and green tangent lines and I found that the angles in blue are equal to theta 1. Also , as the BCD triangle is equilateral, theta 2 = 30. With this I can calculate the side of this equilateral triangle as a function of the radius R of the circumference. After that, I can't go on...
  4. This is Not a Rainbow(by minutephysics)

    This is Not a Rainbow(by minutephysics)

    I'll do a small poem above his one: Roses are red, Violets are blue. As for the rainbow, we have no clue. But @minutephysics is such a good dude. He told us one thing that's always true: Purple in a rainbow is just a supernumerary hue. THE END
    • YoungPhysicist
    • Media item
    • rainbow
    • Comments: 0
    • Category: Optics
  5. S

    How is thermochromatic rainbow paint made?

    I'm curious how thermochromatic paint is made that has many changing colors corresponding to different temperatures? Read that liquid crystals are used but they same as in LCD displays or it's somekind another chemical?
  6. Andy Resnick

    I Recent Rainbow - three supernumerary bows

    Sunday afternoon storms yielded a rainbow: Visible are three supernumerary bows inside the main one; this interference pattern is the result of unusually uniform raindrop sizes.
  7. simon willetts

    Rainbow Curvature: Why is it Curved?

    Jus a brief musing. I understand that light refracts showing the different colours when a rainbow is formed but have never known why they are curved rather than straight. Probably a simple explanation but not known to me. Can anyone explain please
  8. Buzz Bloom

    I What caused a rainbow near the setting sun?

    About a half-hour before sunset I saw part of a rainbow extending upwards from the horizon about 10 degrees. All seven colors from red to violet were visible from left to right, but they were somewhat faded out. What caused this partial rainbow which I saw about 30 degrees north of the setting...
  9. Likith D

    B What type of spectrum is a rainbow?

    maybe it is emission spectrum of the sun but, seems continuous... unlike few distinct lines of the hydrogen emission spectrum...few images i just checked about it are similar to absorption spectrum...then maybe difraction could have made emission spectrum seem so or maybe not... Well I am very...
  10. D

    What is causing the strange light phenomenon in my bedroom?

    Hi ladies and gents! I'm new to the physics community and completely useless in the subject area, however I am extremely interested in physics. After turning off the television just now I noticed something odd. There is a big mirror behind the bed, and the television is on the wall in front...
  11. 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.
  12. 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...
  13. 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
  14. T

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

    I'm interested in rainbows. I'm talking about good old fashioned arc/halo rainbows like those you see in the sky. Sometimes you see rainbows from lawn sprinklers. How small would the smallest rainbow arc conceivably possible to view be? Could I make a rainbow at night using a sprinkler with a...
  15. OmCheeto

    What caused the Quadruple Rainbow?

    I've done this synthetically, in the past. I've never seen a natural set before. I wonder what caused the second set. A lake?
  16. 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...
  17. C

    Exploring the Spectral Differences between Sunlight and Flashlight Light

    In the morning I wake up and there is a amazing light effect that is caused by the sunlight and the chandelier in my living room. However when I use a flashlight to try to duplicate this process I am left with a pathetic duplication. The colors and size in my duplication are non vibrant and...
  18. C

    Can you explain the science behind how a rainbow is formed?

    How is a rainbow formed? Is it a series of droplets that refract the light to our eyes, or is it multiple droplets at different heights where each droplet gives just one color that's visible to us?
  19. wolram

    Exploring Inflation with Rainbow Gravity: A Layman's Guide

    ] arXiv:1310.2072 [pdf, ps, other] Intermediate inflation from rainbow gravity John D. Barrow, Joao Magueijo Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc) It is possible to dualize theories based on deformed dispersion...
  20. Evo

    Rainbow Eucalyptus Tree: Incredible Natural Wonder

    Who knew? http://www.b.weather.com/home-garden/garden/weirdest-trees-earth-photos-20130923?pageno=2
  21. K

    Desktop rainbow experiment help

    Hi, I was wondering if comeone here might be a ble to help me. I am slowly building my daughters various toys, some they're helping me build, others they just play with, but all are essentially science experiments and learning. My eldest has recently become infatuated with rainbows and I...
  22. bigfooted

    What causes rainbow color in heated steel?

    Hi, This question came up after some stainless steel samples were exposed to high temperatures (metal flame holders in a combustion chamber). Some of them had areas with rainbow colors. What exactly happens to the steel that causes these local rainbows? If the colors in point A and B on the...
  23. M

    Has anyone here read Gravity's Rainbow?

    Read it first over the summer last year. Doing it again with a 400 page companion reader to point out all of the allusions. The amount of information contained in this book is mind boggling. I could probably read it 10 times and only retain a fraction of what Pynchon recorded.
  24. B

    Does a black body radiate all colors of the rainbow?

    When a black body is heated the colors listed are IR, red, orange, yellow, white, blue-white, UV. Why doesn't a black body radiate all colors when heated: Red Orange Yellow Green Blue Indigo Violet? And why not shades of these colors?
  25. D

    Rainbow without rain at Stonehenge

    Here is a video that I took on the 14/9/2011 after having an undefined urge to go to Stonehenge. My location was atop the first in the line of mounds that make up the Winterbourne barrows. What you can see is a rainbow formed at sunrise with the sun in direct alignment to the barrows but with no...
  26. H

    Rainbow Shape: Why Is It Always an Arc?

    why is rainbow always an arc?
  27. A

    Maxwell's Rainbow Problem frequency/wavelength

    Homework Statement A certain helium-neon laser emits red light in a narrow band of wavelengths centered at 632.8nm and with a wavelength width if .01nm. What is corresponding frequency width for the emission? Homework Equations f=c/\lambda ? The Attempt at a Solution I tried using...
  28. W

    Is rainbow figure correct ?

    Is rainbow figure correct ?? Homework Statement It's a basic principle that why we see rainbow. I've described information in my attachment. That figure is given by my teacher, he says to find out mistake in it. My attempts I think angles on horizontal lines are incorrect, will...
  29. E

    Understanding Rainbow Dispersion in Glass and Mirrors

    I was just wandering, why when I look through a glass or a mirror at 45 degrees related to it's surface normal I don't see a rainbow/blurry image? Here is a picture that hopefully, describes better what I mean. Dispersion by Cristi .eXPV, on Flickr
  30. L

    Calculating Delta for Red & Violet Light in a Rainbow

    Hi everyone Homework Statement Let's say we observe a rainbow. We know the refraction index of the red and violet light, let's call them n_{1}=1.46 and n_{2}1.47 Now I want to calculate the angle \delta Homework Equations In a square the total angle is 360°, so we have...
  31. H

    I was wondering would it be possible to have more than one rainbow

    I was wondering would it be possible to have more than one rainbow within the same area so another - that two rainbows are over lapping?
  32. C

    Why does a rainbow stay still while it's raining?

    Why does a rainbow look so crisp and stationary if the rain is falling. It seems like it would cut in an out.
  33. B

    Rainbow Spectrum Topology Map to Heightmap Grayscale.

    Hello, I am working with python's Image Library (PIL), Sympy, and Matlab. I have a topographical map of the earth, ( see 3d warehouse from google ). I am wondering if with an rgb matrix from a jpeg heightmap is traditionally the value of black and white ignored, because it seems that the...
  34. P

    How do the colors of the rainbow work

    I know this may sound like a stupid question, but after reading about and even watching an entire MIT lecture on rainbow formation, I just don't understand how the colors of a rainbow can show up separately. Given what I learned about the light paths for different colors in a rainbow, I know...
  35. Dembadon

    Unbelievable Double Rainbow Brings Tears of Joy

    This is probably one of my favorite videos I've ever seen on youtube. https://www.youtube.com/watch?v=OQSNhk5ICTI His passion for this double rainbow is incredible. I think he even starts crying around 1:45 into the video.
  36. L

    Curvature of an Artificial Rainbow (created in Lab).

    I have just created a rainbow artificially and the photo is attached. I didn't expect the bow to come out straight as it has. Does anyone have any idea why it is straight and not curved (or circular)? I know rainbows are normally curved (or spherical) normally because the particles that the...
  37. K

    How does rainbow form? And Light Question

    Hello, I know this is a childish question, but i am still going to ask how does the rainbow form? From my knowledge, rain acts like a spectrum and separates light, which makes the 7 colours but if that is true, why is the rainbow perfectly arched. If my memory serves me correctly, the book "A...
  38. N

    Can a Lens Create a Rainbow from a Broad Beam of Light?

    In standard experiment with prism, you can create a rainbow from a thin beam of white light. Is it possible to design a lens that will create a rainbow from a broad beam? Even if it is only at a fixed distance from the lens?
  39. H

    Titanium rainbow quartz help

    Hi, I am wondering if anyone can help me with a strange request... I am looking to find out if there is any way with the help of an expert I can recreate the same or a similar effect of the rainbow/iridescent effect that is found on titanium rainbow quartz crystals? This could either be on...
  40. P

    Why rainbow has a shape of arc and why its ends are bent down.

    why rainbow has a shape of arc and why its "ends" are bent down. Can anyone explain why rainbow has a shape of arc and why its "ends" are bent down.
  41. J

    The Rainbow Thread: Seeing & Sharing Unusual Phenomena

    A while ago I saw a rainbow while I was driving. The end of the rainbow lay right on the hood of my car. When I came to a stop, I popped the hood to see if there was a pot of gold in there. Of course, by then the rainbow was gone and so was the gold. I said I would post about it, but forgot...
  42. I

    Upside down rainbow seen just before China Quake

    I've just seen footage on U-Tube of a strange rainbow seen in the clouds just before the Quake last week. The colours are in reverse order to the usual after-shower rainbow. My mind tells me that if the colours are reversed then the source of the radiation must be from the opposite direction...
  43. F

    Rainbow table reduction function

    I recently did some personal research into the aforementioned functions. I created a few simple functions based in part on sine (and cosine). Anyway, the basic idea was to get a seed from the sine of some number, since -1 =< sin N =< 1. However, I think that sine is not an ideal function to...
  44. A

    Why does a rainbow form an arc shape?

    We all know as to why we see a rainbow. But why do we see it in a the form a circular arc. Why not a straight line or anything else? I was reading one book and that gave some reason that eyes make the a particular angle at the light from the drops of water. We all know the first part that we...
  45. S

    Rainbow Arc Fraction: Solve the Math Problem

    1. A man stands on a mountain peak 2 km from the ground below, and observes a rainbow 8 km away. What fraction of the arc of the rainbow does the man see? Homework Equations I tried using a triangle to figure this out but I couldn't come any closer to the answer. I know that the rainbow largely...
  46. M

    Is rainbow a prismatic spectrum or grating spectrum ?

    Is rainbow a prismatic spectrum or grating spectrum ? I think it is a grating spectrum as Deviation Order(violet least and red most) is same as that of grating Source is at infinity (sun) Image is at infinity
  47. Ivan Seeking

    Who sings Somewhere Over The Rainbow on YouTube?

    I had heard this and really liked it but had no idea who did it. Good ole UTube. I know that MIH has heard it before. :biggrin: http://www.youtube.com/watch?v=2A2Jt4WOxN8&mode=related&search= Anyway, for some reason I couldn't get it out of my head once I heard it. It's not really...
  48. Mk

    Driving Through a Rainbow: The Truth Behind This Phenomenon

    Is it physically possible to drive through a rainbow? Why or why not?
  49. D

    See a Complete Circle Rainbow: Causes & Conditions

    All the rainbows that appear naturally, are usually semicircles, what is the reason for this, they could also be as little arcs as well. Are there any conditions under which a complete circle of the rainbow may be seen?
  50. zoobyshoe

    Unusual Double Rainbow at Zoobie Brush Shelter

    I caught this picture of an unusual double rainbow yesterday after a shower near the zoobie brush shelter here:
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