From:  "Dennis \(Icarus\)" <nojunkmail@ever.invalid>
Date:  29 Apr 2006 08:06:42 Hong Kong Time
Newsgroup:  news.alt119.net/rec.scuba
Subject:  

Re: You use different lenses underwater because the speed of light is different

NNTP-Posting-Host:  null

"Xiaoding"  wrote in message
news:1146256083.851304.183680@u72g2000cwu.googlegroups.com...
> We need to define our terms:  the word "light" here is being used
> rather loosely.  I define "speed of light" as it's speed in a vaccuum.


That would be "c".

> i define "light" as a single photon.

Cool - I'm using light as referring to electromagnetic radiation.

>
> When you read that the "speed" of light is slowed in a medium, it means
> that the propogation of it is delayed.  However, the speed of one
> photon, as it leaves one atom and goes to another IS NOT SLOWED.  This
> is the source of much confusion, even among scientists!  If I'm wrong,
> let me know, always want to know.  The "delay" is referring to the
> propogation of the wavefront, which is diff. from a single photon.  The
> speed of light does not change, not ever, or Einstein was wrong.  The
> "delay" is caused by atoms getting in the way of the wavefront,
> absorbing it, re-emitting it, etc.  This cocept is never explained in
> the popular press, or the scientific press, either!
>

So if the photon's propagation is delayed, then, in effect, the speed of
that photon is slowed.
In other words, the photon travels less distance, for the same amount of
time, in water than it does in a vacuum.

To me, this would indicate that the velocity of light is different in
different media, since it'd take longer for it to reach the other point when
traveling through that media as oppsoed to a vacuum.

In this context, "speed of light" would be, I think, equivalent to its "rate
of propagation"

Dennis