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From: jfc@athena.mit.edu (John F Carr)
Newsgroups: sci.misc,sci.physics
Subject: Re: differences between sound and light waves?
Message-ID: <3129@bloom-beacon.MIT.EDU>
Date: 21 Feb 88 20:31:28 GMT
References: <413@prlb2.UUCP> <4110@aw.sei.cmu.edu> <6917@agate.BERKELEY.EDU> <4809@ihlpg.ATT.COM> <1181@microsoft.UUCP>
Sender: daemon@bloom-beacon.MIT.EDU
Reply-To: jfc@athena.mit.edu (John F Carr)
Organization: Massachusetts Institute of Technology
Lines: 22
Keywords: macroscopic behaviour

In article <1181@microsoft.UUCP} t-peterw@forward.UUCP (PUT YOUR NAME HERE) writes:
}As far as I know the only thing that travels faster than the speed of
}light is the Starship Enterprise. As a high school student, I spent a summer
}working in a reactor. The workers used to laugh because the guides that 
}would occasionally come through would say that the blue aura around
}a sample of radioactive cobalt in a bay (ie water bay) was caused by
}EM waves travelling faster than the speed of light in water. I believe
}the real cause of Cherenkov radiation is that the speed of light in the
}emitting medium is greater than that of the water so when the EM
}waves enter the water they release enery (in the form of blue light)
}as they assume the speed of light of the water medium.
}
}Please correct me if I should err.

If this were the cause of Cherenkov radiation then you would see a blue
glow coming from glass, which has an index of refraction similar to that
of water.  Energy = h*frequency, and frequency does not change as radiation
changes media.  The blue glow is the result of massive (i.e., not massless)
particles losing energy as they slow to the speed of light in water.


  --John Carr   (jfc@ATHENA.MIT.EDU)