Why Do We Get Rainbows?

A bite-size answer to the question why do we get rainbows…

Image by C. G. P. Grey via Flickr

It’s been raining here again in the UK. But there has been a little sunshine too. On the way home from the zoo last weekend my son spied a beautiful rainbow in the sky up ahead of us and asked “Dad, why do we get rainbows?”

 

So what’s the answer? Well, to begin, we need to know that white light (e.g. sunlight) is actually made up of a spectrum of colours. Light travels from the Sun to the Earth in waves of different colours. Some light travels in shorter or choppier waves whilst others travel in longer or smoother waves. Different coloured light has different wavelengths – red has long waves, blue has short waves. This phenomenon was explained by Sir Isaac Newton by letting sunlight pass through a prism. When the light passes through the prism, it is refracted (bent) and scattered (known as dispersion). And because different coloured light has different wavelengths and frequencies, the amount by which light is bent varies. This means we can see the ‘split’ or spectrum of colours from which white light is made.

 

The above principle can help explain how rainbows are formed. When there are water droplets in the air – e.g. during or following rain – light from the Sun penetrates the surface of the drop, a bit like our prism. As it enters, the light is refracted and dispersed before hitting the back of the drop. Most of the scattered light then reflects or bounces off the back of the raindrop, passes back through the front and is refracted again. What we then see in the sky is our rainbow.

 

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40 Responses to “Why Do We Get Rainbows?”
  1. Mystical Whitewolf Says...

    On February 9, 2011 at 3:13 pm

    Another great explanation to an important question presented by your son! Well done.


  2. anndavey650 Says...

    On February 9, 2011 at 3:16 pm

    It’s amazing what a little bit of rain and some refracted sunlight can achieve!


  3. lillyrose Says...

    On February 9, 2011 at 3:18 pm

    Awwww… going to the zoo and rainbows! Beautiful. Great detail on describing why we have rainbows. I still like to think there is a pot of gold at the end of the rainbow guarded by a big green dragon who is in need of the dentist :-)


  4. Suni51 Says...

    On February 9, 2011 at 3:38 pm

    That’s the reason we see the rainbow.


  5. Farzeela Fee Faisal Says...

    On February 9, 2011 at 3:39 pm

    An interesting read. Good article.


  6. LoveU Says...

    On February 9, 2011 at 4:03 pm

    Great article, I better remember this,as will be asked by my children in future :)
    Thanks!


  7. tonywriter Says...

    On February 9, 2011 at 4:08 pm

    very well defined article mate,That’s the real scientific answer behind rainbow. Thanks very well informative share!


  8. CA Johnson Says...

    On February 9, 2011 at 6:14 pm

    Thanks for letting us know how we get rainbows. I used to wonder where they came from when I was little.


  9. LJ Spain Says...

    On February 9, 2011 at 6:34 pm

    It is a sign from God that He keeps promises too!


  10. leo604 Says...

    On February 9, 2011 at 7:19 pm

    nice post


  11. DaYong Says...

    On February 9, 2011 at 8:06 pm

    thanks for the info!


  12. GameLive Says...

    On February 9, 2011 at 9:00 pm

    interesting stuff


  13. Eunice Tan Says...

    On February 9, 2011 at 9:45 pm

    This writing is as beautiful as rainbow.


  14. LCM Linda Says...

    On February 9, 2011 at 10:19 pm

    Interesting topic. I know how to explain the formation of rainbow now. Many thanks!


  15. lapasan Says...

    On February 9, 2011 at 10:45 pm

    Thanks for the informative article. I enjoy reading it.


  16. wonder Says...

    On February 10, 2011 at 1:20 am

    This is a useful article.


  17. CHIPMUNK Says...

    On February 10, 2011 at 4:44 am

    great work


  18. papaleng Says...

    On February 10, 2011 at 5:46 am

    What a clear and interesting Science lesson. thanks for the valuable inputs.


  19. sathi.k Says...

    On February 10, 2011 at 7:41 am

    This is the best article I have read so far on this optical and meteorological phenomenon. Wonderful thought with detailed explanation. Thank you for creating and sharing!


  20. travelnews Says...

    On February 10, 2011 at 8:09 am

    Wonderful and good thought thanks


  21. Freethinking Says...

    On February 10, 2011 at 9:16 am

    Your article was a great explanation on the beauty of rainbows. I’m still looking for Sean the Leprechaun with his pot of gold at the end of a rainbow. That is if it ever stops snowing here in the northeastern U.S.


  22. pruelpo Says...

    On February 10, 2011 at 10:44 am

    love this dude interesting share.


  23. Cinders Says...

    On February 10, 2011 at 11:25 am

    Great explanation especially about the wavelengths of light, very clear.


  24. Terrie Schultz Says...

    On February 10, 2011 at 2:00 pm

    Good explanation!


  25. tiffi Says...

    On February 10, 2011 at 4:40 pm

    Very good share! Great job!


  26. lonelyplanet Says...

    On February 11, 2011 at 2:16 am

    I love watching rainbow in rainy days.


  27. Lady Sunshine Says...

    On February 11, 2011 at 4:18 am

    Rainbows are lovely, esp after a rainy day. Thanks for the explanation.


  28. rejarol Says...

    On February 11, 2011 at 4:53 am

    Yeah, it’s a concept of refraction, dispersion, and scattering in Physics. In the bible, it symbolizes God’s covenant with man.


  29. janesteban Says...

    On February 11, 2011 at 12:56 pm

    Great article and really well explained. Thanks for sharing.


  30. Tulan Says...

    On February 11, 2011 at 2:03 pm

    i love rainbows, I used to go out in search of them after every rain storm.


  31. Kathy Morelli LPC Says...

    On February 11, 2011 at 5:20 pm

    Nice article!!


  32. GameLive Says...

    On February 11, 2011 at 9:41 pm

    good share


  33. Betty Carew Says...

    On February 12, 2011 at 11:47 am

    Aweeee Stable I think myself so lucky each time I see a rainbow. Thanks for a very informative share. Rainbows help to create memories like your trip to the zoo.


  34. Patrick Regoniel Says...

    On February 13, 2011 at 8:48 am

    They say there is a pot of gold at the end of the rainbow.


  35. shelpeare Says...

    On February 13, 2011 at 10:27 pm

    Thanks for the info. God used these natural means to show His covenant with man in Gen. 9.


  36. mtrguanlao Says...

    On February 16, 2011 at 1:13 am

    You enlightened me about it,thanks for the clear explanations!


  37. cometbballgrrl Says...

    On February 16, 2011 at 7:02 pm

    Very good explanation!


  38. Brewed Coffee Says...

    On February 16, 2011 at 9:08 pm

    I always take long moments to admire rainbows because I don’t get to see them everyday. It’s really cool to know the science behind rainbows.


  39. nz2rdfox Says...

    On February 21, 2011 at 9:10 pm

    One of the many reasons why I love to read your articles..it always add something new to your reader’s knowledge..

    thanks for educating as always :)


  40. genicuta Says...

    On February 28, 2011 at 5:48 am

    Good article,thanks…


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