XPost: alt.usage.english, sci.physics   
   From: robban1@bigpond.com   
      
   On 10/08/11 3:36 AM, David Hatunen wrote:   
   > On Tue, 09 Aug 2011 18:13:40 +0100, Jonathan de Boyne Pollard wrote:   
   >   
   >>> Our TV sets can show only three colours, [...]   
   >>   
   >> Apart from the ones with the latest gimmick: yellow.   
   >>   
   >>> A hypothetical Martian with four kinds of colour receptors [...]   
   >>   
   >> Of course, one doesn't have to go to Mars to find a creature whose   
   >> visual apparatus differs from that of a human.  The humble honey bee can   
   >> see into the ultra-violet, having receptor cells for ultra-violet, blue,   
   >> and green.  Some butterflies and wasps have a four-colour receptor   
   >> system: ultra-violet, blue, green, and red.   
   >>   
   >> Moreover the differences are not just in the types of receptors, but   
   >> also in how they are wired up.  Some insects, including honey bees, have   
   >> been shown to only respond to motion via the green receptors, for   
   >> example.   
   >   
   > Ultraviolet light is light of shorter wavelength (higher photon energy)   
   > than visible light, but the boundary between the two is not specifically   
   > defined: sort of "about 400 nm".   
   >   
   > When I had my natural eye lenses replaced with plastic lenses I was told   
   > I would be ale to  a teeny bit into the ultraviolet, the plastic being a   
   > little more transparent to it than my natural lens had been [*], but I   
   > never did anything to determine to just what photon energy I could see.   
   >   
   > [*] Of course, by the time I had the replacements done the cataracts in   
   > my natural lenses turned everything a yellowish hue. When the bandages   
   > first come off the first impression is that everything is intensely   
   > bluish, kind of like those irritating auto headlights.   
   >   
      
   Please don't frighten me. I've just done a trial of a hearing aid that   
   made everything sound like a tape-recording - mainly chairs squealing,   
   doors slamming, engine noises - basically, unbearable. And on the 17th I   
   am having cataract surgery. I have already been warned that, until the   
   other eye is done, I may have considerable difficulty, and now you tell   
   me I'm going to get the blues as well.   
      
   --   
   Robert Bannister   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)