[Tfug] Another OT Optics Question

[eric christian]

>
> Date: Sun, 3 Aug 2008 12:43:29 -0700 (PDT)
> From: Bexley Hall <bexley401 at yahoo.com>
> Subject: [Tfug] Another OT Optics Question
> To: tfug at tfug.org
> Message-ID: <735082.29930.qm at web32902.mail.mud.yahoo.com>
> Content-Type: text/plain; charset=us-ascii
>
> OK, zero-th order understanding of how rainbows manifest
> themselves...  :>
>   
Newton's terms...
> Inceident ray comes back ~40 degrees refracted (and reflected).
> So, can I think of rainbow as a "conic section" in a cone with
> a 42 degree apex?
>
> And, the apparent "diameter" of the rainbow is a function
> of how far the water is from the observer?  E.g., a rainbow
> thrown from the mist of a gargen hose would appear to have a much
> smaller diameter than one from water vabor many miles distant.
>
> (I'm not looking for "6 decimal places", here... just a crude
> understanding of the geometry involved  :>  )
>   
You are standing in front of the water drops that are refracting ~41 deg 
the rays of the sun. Thus, the n rainbows will be coming to you, the 
rays split around  ~41 deg . Does it make sense to pose this "diameter" 
of the rainbow arc of the conic section as a function of the distance to 
these drops of water? Probably, this diameter will be a function of the 
length (area) of the water drops and projective geometry will be of help 
here.
Eric