Dear Alessio,
This is a nice demonstration and is part of the physical basis behind the H.G Wells story “The
Invisible Man” – see chapter 19:
“And if you put a sheet of common white glass in water, still more if you put it in some denser
liquid than water, it would vanish almost altogether, because light passing from water to glass is
only slightly refracted or reflected or indeed affected in any way.”
Of course by density he means optical density rather than mass density. This might be a good
starting point for a discussion on invisibility and how it might be possible scientifically. If you
were invisible in air how visible would you be in water? What about in different coloured light? What
would you need to do to make a non-transparent object invisible? Meta materials – here we come!
Something else to consider is that because you can more easily see the test tube in some situations
then this means that light is being reflected/refracted and lost from the "direct line of sight".
This could introduce the idea of an optical coating on a lens to improve performance (your camera
lens will probably have a slight purple colour to it). I believe moths' eyes have antireflective
microstructures to achieve the same effect, although here it is to stop reflections giving them away
to predators.
Kind regards
Chris
------------------------------------------
Dr Chris Robbins
Why Learn That
Tel: 01663 749785
email: [log in to unmask]
www.whylearnthat.co.uk
------------------------------------------
23:04
Thursday 06 January 2011
> Hi All,
> This blog post shows a really cool demonstration on refractive index I have
> seen today.
>
> http://alessiobernardelli.wordpress.com/2011/01/06/refraction-index-magic/
>
> <http://alessiobernardelli.wordpress.com/2011/01/06/refraction-index-magic/
>>Please have a look and let me know what you think.
> Thanks,
> Alessio.
>
>
> Alessio Bernardelli
>
> IoP Network Coordinator
> 109 Maes Y Coed Rd
> Cardiff
> CF14 4HE
>
> Tel: 02920315988
> Mobile: 07527528088
>
> Blog: alessiobernardelli.wordpress.com
> Twitter: twitter.com/aso.ber
>
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