jsw@hou2h.UUCP (J.SOLTES) (11/10/84)
<Nothing is foolproof. Fools are too ingeneous!> > The postulates were inspired by the fact that light waves propagate in > a vacuum (as predicted by Maxwell's equations), which is really a fairly > strange thing for waves to do -- normally waves are simply disturbances > (compression/expansion) of the media through which they propagate. Which reminds me of something else that has been bothering me since high school physics: if light does not propagate by 'disturbing' a medium, why does light travel at different speeds through different substances? (i.e., why does light refract through a lens or a prism and why do you get the illusion of a 'broken' pencil when you stick one in a glass of water?) John Soltes AT&T Consumer Products hou2h!jsw "A little knowledge is a dangerous thing. Go to school. Get a little knowledge. Live dangerously."
sra@oddjob.UChicago.UUCP (Scott Anderson) (11/10/84)
<<<<<<< > Which reminds me of something else that has been bothering me since > high school physics: if light does not propagate by 'disturbing' a > medium, why does light travel at different speeds through different > substances? (i.e., why does light refract through a lens or a prism > and why do you get the illusion of a 'broken' pencil when you stick > one in a glass of water?) Light travels at slower speeds through material substances because it is being absorbed and coherently reemitted. This, in effect, slows it down. The refraction occurs because, when passing between two substances, different points on a wavefront will travel at different speeds, which 'bends' the wavefront: > Air | Water (or other liquid refreshment) > | > | > | > | > | > | >| | > | > | > | > | > | > | > | > (Does this qualify as a doodle?) Something in two different media, such as a pencil partially in water, will have part of its image shifted by the refraction, and will therefore appear 'broken'. _, Scott Anderson 3~ ...!ihnp4!oddjob
gwyn@brl-tgr.ARPA (Doug Gwyn <gwyn>) (11/11/84)
> ... if light does not propagate by 'disturbing' a > medium, why does light travel at different speeds through different > substances? (i.e., why does light refract through a lens or a prism > and why do you get the illusion of a 'broken' pencil when you stick > one in a glass of water?) But light DOES interact with matter (electrons) if it's there. It need not be there for light to propagate, was the point.
merrill@rex.DEC (11/13/84)
Michaelson & Morley setup an elegant experiment to measure the earth's velocity through the "either" that was the "medium" in which light travelled. Their Negative findings proved that (a) the "either" was non-existant and (b) that the speed of light was the same in any direction [ and therefore in any coordinate system ]. (Encyclopedia of Mathematics) Light propogates as TWO sets of waves: one electrical field, and one magnetic field. As the magnetic field colapses it creates an electrical field; as the electrical field colapses it creates a magnetic field, and VOILA THE light propogates without benefit of media. Now while the mathematics makes the speed of light appear the same in any coordinate system, engineering the experiment requires detecting either or both electrical and magnetic fields [so what?] so you actually detect the frequency of the signal [should have said "A frequency"]. So if the "boys and girls chasing each other and firing lasars" are racing through space and using the same ruby lasars, what frequencies will they appear to receive??? Please let them stay in space because if their light beams go through air the air molecules will interact with the elec-magn fields and slow down the light [what if anything happens to the "frequency"?]. Rick Merrill decwrl::rex::merrill