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At the Exploratorium, Pete Stephens has been filling our spaces with
dispersed color spectra ("rainbows") for many years, using fairly
inexpensive slits, mirrors and diffraction films.  The colors are bright
and vivid when they're the dominant light, but can look washed out if
they're competing with other bright lights on the same surface.  Pete's not
on this listserv, but he gave me permission to post his e-mail address for
anyone wishing to contact him for details at [log in to unmask]

Some examples can be seen at *http://tinyurl.com/CGColors* and *
http://tinyurl.com/CGColors2*


On Thu, May 30, 2013 at 1:24 AM, Ian Russell <[log in to unmask]> wrote:

> ISEN-ASTC-L is a service of the Association of Science-Technology Centers
> Incorporated, a worldwide network of science museums and related
> institutions.
>
> *****************************************************************************
>
> Regarding water-filled prisms, I have discovered that you can only get a
> sufficiently dispersed spectrum with a 90-degrees prism. The refractive
> index of water is significantly less than that of glass. So although a
> 60-degrees prism bends a narrow beam of white light nicely, it doesn't
> spread out the colours enough to show them clearly.
>
> That was why I recommended a rectangular fish tank. You can create a
> spectrum in two different ways with this setup. You can bend a vertical
> 'slit' of light sideways through one corner of the tank onto a vertical
> wall
> or screen. Or, as I suggested, you can bend a horizontal 'slit' of light
> downwards, using the 'prism' formed by the water surface and the side of
> the
> tank.
>
> It really is effective, provided that you project a narrow, focused 'slit'
> of very bright light. The incident light-beam must enter the water surface
> at a low, grazing angle and the emerging beam shines downwards at a similar
> angle, very close to the side of the tank.
>
> Glass or Plexiglass tanks work equally well.
>
> Promoting public engagement with science
> through a contagious delight in phenomena
> *
> [log in to unmask] * http://www.interactives.co.uk
> *
> http://uk.linkedin.com/pub/ian-russell/0/636/305
> *
> Give people facts and you feed their minds for an hour.
> Awaken curiosity and they feed their own minds for a lifetime.
> *
> Ian Russell
>
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