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Desktop rainbow experiment help

  1. Aug 4, 2013 #1
    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 recall a science experiment I did at school to re-create a rainbow with a light and dripping tap, however I cannot remember the specifics. All my searches on-line show how to project a rainbow on to a piece of paper or wall, however I'd love to show (on the table top) a rainbow in the air.

    I know you can do this with a hose on a summer's day, and a know the 42° angle needs to be incorporated somehow, but if I could create the effect in miniaiture, available at any time, then perhaps I can make a water feature with 12v halogen lamp in it, so when it turns on, there's their very own rainbow created. :)

    From my research already I'm thinking I may have over-stretched myself here, but can't stop the nagging feeling that it can be done, can anyone point me in the right direction, or at least tell me I'm crazy so I can move on to the next idea? ;)

    Many thanks
  2. jcsd
  3. Aug 5, 2013 #2

    Simon Bridge

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    You need the light to come from the same direction as the observer.
    Apart from that, a fine mist will produce a rainbow for you - you'll need to fiddle around a bit.
    Experiment in a dark room.
  4. Aug 5, 2013 #3
    I would further recommend either an old-style incandescent light source, or a newer "xenon" HID light. Avoid energy saving light bulbs, their spectrum may be very poor for a good rainbow.
  5. Aug 5, 2013 #4


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    I used the search terms "rainbow experiments for kids" in Google and found LOTS of ideas and experiments you can do at home to create rainbows. Probably you can find a suitable one there.
  6. Aug 5, 2013 #5
    Thanks for the advice everyone. Like I said in the OP, I have trawled google but all techniques either project a rainbow pattern into a wall/paper/floor or involve being outside in a sunny day with the hose.

    I really wanted an indoor 'live' rainbow for want if a better phrase.

    I will tinker with some spritzer bottles and lamps and see how I go. Failing that I may just use the very simple projection method instead.
  7. Aug 6, 2013 #6


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    To get a good rainbow you need one dominant light source. Even with the Sun as a light source, to get a good rainbow you need dark clouds or a shaded hillside to avoid too much extraneous light dilution. I suggest that the experiment could work in a shower cubicle, with the lights out and using a good sharp torch (Maglight quality with a filament bulb in it). A black cloth or even a bin bag would make a good background. You will have a hard job doing better than a hose in the garden, I think. How about making a fine spray (from a plant 'mister' or bicycle pump full of water) and firing it out of a window at night, with a torch as light source?
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