• Question: Where do rainbow come from?

    Asked by emmagrace to Dalya, Derek, Sarah, Tim, Tom on 19 Jun 2011.
    • Photo: Tim Millar

      Tim Millar answered on 17 Jun 2011:

      White light is made of different wavelengths of light. Rainbows are formed when raindrops split the white light into its component parts because they are acting like prisms and defracting the light. Some light is diffracted more than others so we see the colours of the rainbow spread out across the sky.

    • Photo: Derek McKay-Bukowski

      Derek McKay-Bukowski answered on 17 Jun 2011:

      Careful Tim, that’s not quite right!

      The optical effect is “refraction”, not “diffraction”.

      Refraction is an effect where the speed of light INSIDE the water droplets is different to the speed of the light OUTSIDE. If the light goes straight in, that’s fine, but if it goes in at an angle, then the light changes direction slightly. Because the speed of light across that air-water boundary is different for different colours, the colours start heading in different directions. Thus the white light “splits” into the colours.

      There is an effect called diffraction too, but this has nothing to do with the colours in the large rainbows we see in the sky. Instead, diffraction comes into effect when the light passes around solid obstructions, causing things like diffraction patterns or solar glories.

    • Photo: Tom Crick

      Tom Crick answered on 18 Jun 2011:

      A rainbow is a meteorological phenomenon that causes a spectrum of light to appear in the sky when the Sun shines on to droplets of moisture in the Earth’s atmosphere and always appear in the section of sky directly opposite the sun.

      For there to be a rainbow you need water drops in the air and sunlight shining from behind at a low altitude angle — this is not always the case when there are clouds!

      But when it is sunny, you can usually always see rainbows where there is falling water e.g. waterfalls and fountains.

    • Photo: Sarah Thomas

      Sarah Thomas answered on 19 Jun 2011:

      To make a rainbow you need moisture in the sky, specifically rain clouds and several holes in those clouds to allow the sunlight to come through. Rainbows are seen because the sunlight shines through the raindrops and distributes throughout the moisture showing the rainbow color spectrum. You can also see rainbows in the mist of a waterfall, a wave spray at the ocean or even in water sculpture located outside.

      You can make your own rainbow at home! Be sure the sun is shining on the location you want to create your rainbow. Turn on a sprinkler or the garden hose with a wide open spray and set up the spray to continue while you walk away.

      You should now be able to see a lovely rainbow! Quick get your camera out!!

      🙂

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