Path: utzoo!mnetor!uunet!husc6!bbn!uwmcsd1!ig!agate!ucbvax!ernie.Berkeley.EDU!jwl
From: jwl@ernie.Berkeley.EDU (James Wilbur Lewis)
Newsgroups: sci.misc
Subject: Re: differences between sound and light
Message-ID: <22910@ucbvax.BERKELEY.EDU>
Date: 6 Feb 88 20:30:09 GMT
References: <413@prlb2.UUCP> <4100002@osiris.cso.uiuc.edu>
Sender: usenet@ucbvax.BERKELEY.EDU
Reply-To: jwl@ernie.Berkeley.EDU.UUCP (James Wilbur Lewis)
Organization: University of California, Berkeley
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In article <4100002@osiris.cso.uiuc.edu> sparrow@osiris.cso.uiuc.edu writes:
>>As I am thinking about differences between vision and audition, I would like
>>to know the difference of behaviour between light waves and sound waves which
>>manifest themselves at our everyday (Newtonian, non-quantum) scale. 
>
>  I also know for a fact that
>your ears are very sensitive over a large range of sound intensities,
>many orders of magnitude.  I suspect that your eyes are not sensitive
>to several orders of magnitude of light intensity (how bright or dim),
>but I am less sure of this.

No, you're mistaken about this...the full moon is about 1,000,000 times
brighter than the faintest stars that are visible without optical aid;
typical sunlit terrestrial scenes are brighter still, by perhaps another
order of magnitude.

>For sounds less loud, linear theory holds and you get the same 
>reflection, diffraction, and refraction effects as you do for light,
>just that the scales of things are different.  Remember light travels
>at 3x10**8 m/sec and sound at about 343 m/sec.

This manifests itself in several observable ways...for example, the
Doppler effect is significant for sound, but not light.  ("But officer,
that traffic light looked *green* to me...must have been the Doppler 
effect!" :-)  And the difference between the speed of sound and the speed
of light gives you something interesting to do if you're stuck in a
thunderstorm....

-- Jim Lewis
   U.C. Berkeley