IMHO "optically more dense medium" is bad (non-useful) terminology.
Substitute "a medium of higher refractive index", or perhaps "a medium of
slower light propagation speed".
The misnomer which you cite probably arises as a generalization of the
fact that light travels fastest (and the refractive index is smallest) in
vacuum - so that any transparent material (of non-zero density) is a
slower medium for light propagation.
Or:
One often compares the "optical path lengths" (sum/integral of physical
lengths weighted with refractive index) of ray trajectories. Two
trajectories of equal physical length but different optical path length
may thus (metaphorically) be said to differ in "optical density".
Bob Sciamanda
Physics, Edinboro Univ of PA (em)
trebor@velocity.net http://www.velocity.net/~trebor
----- Original Message -----
From: "julie" <jquah@PACIFIC.NET.SG>
To: <PHYS-L@lists.nau.edu>
Sent: Friday, April 20, 2001 10:41 AM
Subject: Optical density
Dear all,
We often say that light refract towards normal when it enters an optically
denser medium. What exactly is meant by öptically denser? I know it is not
the same as the normal usaga as in glass is denser than air. So what is
the difference?