[time-nuts] John Vig elected President of IEEE

Bruce Griffiths bruce.griffiths at xtra.co.nz
Mon Dec 10 16:58:36 EST 2007


Peter Vince wrote:
> Hi Said,
>
> 	Do you mean this PowerPoint file:
>
> 		http://www.ko4bb.com/Timing/Vig-tutorial%208.5.2.0.ppt
>
> 	Regards,
>
> 		Peter Vince
>   
Using the term diopters on page 4-57 is potentially confusing.
Presumably he means the so called opthalmic (spectacle) industry
"diopter" tools were used to generate the curves.
The term diopter strictly means the reciprocal of the focal length
(measured in meters) of a lens.
The focal length of a thin lens depends on its refractive index and the
curvatures of its surfaces.
A spectacle industry 1 diopter tool will generate the convex surface of
a planoconvex lens with a power of 1 diopter (1m focal length) when the
refractive index of the material used is ~1.52.

Since the none of the refractive indices (1.54421, 1.55333 @ 600nm) of
crystalline quartz are equal to 1.52, labelling the curvatures in this
way is potentially misleading.

Bruce



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