v = (lambda)(nu)    (a wave's velocity = its wavelength * its frequency)

  p = h/(lambda)      (a wave's momentum = Planck's constant / its wavelength)

Waves are one way to move energy from one place to another without having to
move any matter along with it.  Instead, the matter moves back and forth,
or up and down, or side to side, and the energy "travels" from one piece of
matter to another, along a chain of "waving matter" as it moves.  When we
speak of the speed or velocity of a wave, we're talking about the speed that
the energy moves, not the speed at which the matter moves.

We've all seen waves on a lake or pond, or even in a bathtub.  The distance
from one crest to the next is called the wavelength, and the number of waves
that pass any specific location over a period of time is called the frequency.
Wavelength is measured with any unit of length (e.g. meter), while frequency is
typically measured with the unit "per second," as in "10 wave crests pass this
point per second."  Since "per second" is a little awkward to say, we sometimes
call the unit of frequency "cycles per second" in conversation.


It turns out that, because of quantum mechanics, all particles in the universe 
travel in waves.  The wavelengths are microscopically tiny, however, so we don't
see these waves unless we're studying the atomic realm.  This is the basis of
the second equation above, which was first derived by Louis de Broglie 
to describe the wavelike properties of any
particle (massive or massless).  Remember that the momentum of any particle is
its mass times its velocity.

For reference, h = 6.63 * 10^-34 Joule sec.
The speed of a light wave is c = 3 * 10^8 m/sec.