• Question: Since clouds contain tiny water droplets, why are rainbows not permanently present?

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

      Dalya Soond answered on 17 Jun 2011:

      Clouds are pretty…uh, cloudy so it would be difficult to see light diffracting off the water droplets when they are in the clouds.

      However, when the air (which, as you know, is transparent) is filled with misty water droplets, then you can notice the rainbow.

    • 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: Derek McKay-Bukowski

      Derek McKay-Bukowski answered on 19 Jun 2011:

      Dalya is right. It is because the clouds are cloudy!

      To be a bit more technical about it, the density of particles in a cloud is quite high, so even though there are “rainbows” being formed, only the ones at the very surface of the cloud has got a chance of getting out! Additionally, the big white cloud is reflecting lots of lights anyway, so the super weak rainbow is drowned out and we simply don’t see it.

      However…

      It is still possible to get rainbows in clouds. These are called “fire rainbows” or “circumhorizontal arcs”. But they do require special conditions, such as very thin cirrus cloud.

      Try looking up circumhorizontal arcs for some photographs. Here’s one to get you started… http://en.wikipedia.org/wiki/Circumhorizontal_arc

    • Photo: Tim Millar

      Tim Millar answered on 19 Jun 2011:

      There are also sundog, ice crystals giving a halo effect around the sun

      http://en.wikipedia.org/wiki/Sun_dog

    • 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!! 😀

Comments