Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site bnl.UUCP Path: utzoo!watmath!clyde!burl!ulysses!bellcore!decvax!linus!philabs!sbcs!bnl44!bnl!stern From: stern@bnl.UUCP (Eric G. Stern) Newsgroups: net.physics,net.astro.expert Subject: Re: FP inretforometer Message-ID: <187@bnl.UUCP> Date: Sun, 26-Jan-86 14:15:28 EST Article-I.D.: bnl.187 Posted: Sun Jan 26 14:15:28 1986 Date-Received: Sat, 1-Feb-86 05:57:56 EST References: <1917@saber.UUCP> Distribution: net Organization: Physics, SUNY StonyBrook Lines: 35 Xref: watmath net.physics:3806 net.astro.expert:200 > I just heard a discussion of a Fabre Preot interformeter. It involved the > use of 2 mirrors that had 95 % reflectance and 5 % transmission they were > set up parrellel to each other and a given number of wavelengths apart. > It was stated that if this device was raidated with 1 watt of light at that > waveleignth the output at the other end would be 1 watt. And that there would > be 20 wats of energy raidateing back and forth between the mirrors. > Is this realy true and if so how does it work???? > > Name: John Cincotta > Mail: Saber Technology, 2381 Bering Drive, San Jose, California 95131 > AT&T: 435-8600 > UUCP: ...{decvax,ucbvax}!decwrl!saber!jc > ...{amd,ihnp4,ittvax}!saber!jc The major problem with this statement is that the energy content of the Fabry-Perot cavity cannot be expressed in watts since watts = energy/time is a unit of power. The power into the FP system is equal to the power out of the system except for losses in the mirrors and walls. Since the system you describe has equal mirrors on both ends, the power coming out of the cavity must be the same on both the front and back sides. Assuming that no absorption takes place and that 1 watt of power enters the cavity, then 0.5 watt must leave the cavity on either side. Now look in particular at one of the mirrors. Since the mirror is 5% transmitting and 0.5 watts is transmitted through the mirror, then 10 watts must be incident on the mirror which is 20 times the transmitted power. There is no great mystery in this. You can't fool me young man, Eric G. Stern it's turtles all the way down! Dept. of Physics, SUNY stern@bnl.arpa stern@bnl.bitnet BNLCL{1-4}::STERN (HEPnet)