[mythtv-users] Way OT: Wave propagation in mediums

[Ben Kamen]

On 2011-07-13 8:28 AM, Jay Ashworth wrote:
> ----- Original Message -----
>> From: "David Watkins"<watkinshome at gmail.com>
>
>>> The NVP (nominal velocity of propagation) for a copper pair is
>>> typically in the order of 70% of the speed of light in a vacuum. When
>>> testing copper cable, to get an accurate length you need to set the
>>> NVP in the tester - either by using a manufacturers figure, or by
>>> testing a sample of cable.
>>>
>>> And for fibre, yes you are correct.
>>
>> ... which also happens to be approximately 70% of the speed of light
>> in a vacuum.
>
> Color me surprised; he's right; I'm wrong.
>
>    http://www.cable360.net/ct/sections/columns/broadband/45766.html

Yep - this a common thing for us EE types...

http://en.wikipedia.org/wiki/Velocity_of_propagation
http://en.wikipedia.org/wiki/Optical_fiber

The math isn't even all that fancy.