🚀 go-pugleaf

In article <1992Sep23.071825.4702@hplb.hpl.hp.com> davids@spira.bri.hp.com (david sixsmith (contractor)) writes:
>
>Could anyone answer for me the following questions
>
>1. What is (are) the inherent qualitie(s) of a substance, such as glass,
>perspex, diamond, & water, which make it transparent ?
>
>2. What is the mechanism which makes the speed of light lower when travelling
>in such a medium as opposed to traveling in a vacuum ?
>
Well, the answer to (2), in a simple, concise word, is density.  Its about the same reason why you can't run as fast in water as you can on land - the water is denser than the air, therefore you move slower through it.  The speed of light is (frequency * wavelength).  This is about 3 X 10^8 m/s in a vacuum and slower in other media.  When light travels from say air to water, its wavelength becomes shorter and thus the speed of the light (wave) is lowered.  The frequency of a wave (or wave packet) cannot ch


ange once it has began moving.  You can change the frequency at the source but that affects the waves that propoget behing the wave in question.  Anyway, when the wave enters a new medium, its wavelength will change based on the characteristics of thenew medium and thus the speed of the wave will change.

I'm sure all of this is explained better and in more detail in a quantum mechanics class, but I haven't got that far yet.  I'm just in waves and optics now.  QM comes next semester.  QM probably explains question 1 but I don't really know.

>Thanks
>
Sure, anytime.  Hope I helped.  If anyone can add to or correct what I said, feel free.  I do get my physics mixed up at times :)


-- 
*******************************************************************************
*  "My neural pathways have become accustomed    |    Alton R. Pouncey II     *
*   to your sensory input patterns."             |  train@ccwf.cc.utexas.edu  *
*******************************************************************************