Re: Do electromagnetic waves have a measure of entropy?

Entropy is just a measure of the number of different states
accessible to a system.  If your system (e.g., the entire
universe) consisted of nothing but a single electromagnetic
plane wave, the entropy would not increase - it would stay
the same, since nothing changes (i.e., only one possible
state for the universe).  Entropy does not always increase,
it just never decreases - and remember that this is only a
"law" in the statistical sense.  For example, if you have a
very large number (say 10^26) of interacting particles, the
probability that you would ever observe the entropy to decrease
is so small that it is effectively zero.  However, for a few
particles, this may not be the case, though on average (over
a long time period), you would not see a decrease in entropy.

Also, this only applies for CLOSED systems.  Clearly you can
decrease the entropy of a subsystem - otherwise you'd never
be able to make ice cubes from liquid water (or liquid water
from steam, etc.)  The process of freezing water decreases the
entropy of the water, but increases the entropy of the universe
as a whole due to the heat being extracted from the water and
radiated away.  A similar argument applies to living organisms.
A living organism has the ability to highly organize material
that it takes in, but only at the expense of other byproducts
(heat, CO2, etc.) that generate a net increase in the entropy
of the universe.

So, no, living organisms do not violate the "law of entropy",
better known as the second law of thermodynamics.