Why are rainbows bow shaped?

9 Answers

  • Anonymous
    7 days ago

    If they were box-shaped, they'd be called rainboxes!  🌈

  • Anonymous
    1 month ago

    wrong forum.  belongs in physics

  • Funnel
    Lv 5
    1 month ago

    All these good answers very informative of the basic but still doesn't answer why rainbows have the distinct perfect circle or why each ring retains a certain color. Very good question. The shape? It's a circle half hidden by the curvature of earth. The earth is round, ball shaped. But why do the distinctly positioned refractive raindrops turned to that specific color in remain turned to one color in specific rings? Do I have to ask this question on this sight now? Wish we had the comments section back.

  • Dixon
    Lv 7
    1 month ago

    It is the locus of a particular angle between your eye and the sun. So in a 3D space this angle locus effectively rotates around the line from you to the sun. But that generally puts half of it underground, so we just see the top half.

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  • Steven
    Lv 7
    1 month ago

    Rainbows are seen at the intersection of two cones that originate from your eye and the sun. This is where the angle between a line to your eye and another line to the sun create the  42 degree angle of refraction in water droplets. Because that angle depends on the color of light, the cone is slightly wider for red vs green vs violet.

  • 1 month ago

    "...Rainbows get their round shape from a process called reflection. Flickr/Luigi Mengato, CC BY

    Curious Kids: Why are rainbows round?

    Ben Buchler, Australian National University

    August 30, 2017 6.09am AEST

    This is an article from Curious Kids, a series for children. The Conversation is asking kids to send in questions they’d like an expert to answer. All questions are welcome – serious, weird or wacky!

    Why are rainbows round? – Georgina, age 5.

    This is a really complicated question. It’s a hard thing even for many adults to understand. To answer your question, I have to explain two things – refraction and reflection.

    Refraction gives you the colours of the rainbow, and reflection gives you its round shape.

    Refraction and colour

    When you are out on a bright sunny day, it may look like sunlight is all one colour. But in fact, the white sunlight you see is made up of many different colours of light mixed together.

    But what are different colours of light? In fact, light is a wave. Light waves come in different sizes called “wavelengths”. Every colour has a different wavelength. For example, violet light has a much shorter wavelength than red light.

    Every colour of the rainbow has a different wavelength. Wikimedia Commons

    The next thing to know is that when light enters water at an angle, it changes direction. This is called “refraction”. You can see this every time you look into a pond. Ripples on the water make everything under the water look wonky. This is because the light bends as it goes between the air and the water. The amount the light bends depends on its colour.

    Sunlight is refracted and reflected by a water drop.

    The shorter the wavelength of the colour, the more it changes direction. So violet light changes direction more than green light. And yellow light changes direction more than red light.

    Refraction is why all the colours in the sunlight end up separating when it hits the water drop, and we are then able to see all the colours of the rainbow.

    Reflection and shape

    Now we can move onto why rainbows have a round shape. The final thing that happens when sunlight hits a raindrop is that some of that light bounces back, or is “reflected”.

    So when you see a rainbow, you’re actually seeing light that has hit a raindrop and bounced back onto your eye.

    Here’s where we need to get stuck into some maths. In raindrops, sunlight bounces back, or reflects, most strongly at a certain angle - 42 degrees.

    As long as the angle is right, then the light will be reflected and you see a rainbow.

    If we draw rays of sunlight that reflect at 42 degrees into your eyes then those rays start to look like they form a circular arc in the sky. So the reflection gives you the shape of the rainbow, while the refraction gives you the colours of the rainbow.

    If you are standing on the ground, then the rainbow stops when it hits the ground. If you are lucky enough to look out on some rain from a plane, then instead of seeing just a part of the circle, you may be able to see a complete circular rainbow, like this:

    From the air you can see circular rainbows.

    If you like rainbows – and who doesn’t – then there is a whole website full of them here. This site shows many examples of different types of rainbows and other natural light shows that happen as sunlight is refracted and reflected by the Earth’s atmosphere.

    Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to us. They can:

    * Email your question to curiouskids@theconversation.edu.au

    * Tell us on Twitter by tagging @ConversationEDU with the hashtag #curiouskids, or

    * Tell us on Facebook

    Please tell us your name, age, and which city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! We won’t be able to answer every question but we will do our best.

    Comment on this article

    Ben Buchler

    Associate professor, Australian National University

    Ben Buchler does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

    Australian National University provides funding as a member of The Conversation AU.

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  • 1 month ago

    Nice question!

    Rainbows are what you see when sunlight goes into far away water droplets in the atmosphere and bounces back to your eyes.

    The reason why the rainbow is curved is because all the angles in the water drop have to be just right for the drop to send some sunlight to you, standing on the ground.

    So, with the sun behind you, only those water droplets that have the same angle formed by you, the drop, and the sun (about 40-42 degrees) will make the rainbow.

    The rainbow is curved because the set of all the raindrops that have the right angle between you, the drop, and the sun lie on a cone pointing at the sun with you at one tip.  

    The rainbow is the faraway section of that cone shape that you are able to see based on your elevation.  From an airplane, you could see the whole ring at the end of the cone shape.

    The rainbow is colored because the water drops act like little prisms -- how much the light bends when it enters and exits the drop depends on its color.

  • 1 month ago

    In a plane, they can be circular.

  • Anonymous
    1 month ago

    When seen from space they’re actually a full circle. I guess I can’t explain why. Probably has something to do with physics. 

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