Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site jhunix.UUCP Path: utzoo!linus!philabs!cmcl2!seismo!umcp-cs!aplcen!jhunix!ins_apmj From: ins_apmj@jhunix.UUCP (Patrick M Juola) Newsgroups: net.sci Subject: Re: Questions on PHOTONS Message-ID: <1126@jhunix.UUCP> Date: Fri, 8-Nov-85 13:09:33 EST Article-I.D.: jhunix.1126 Posted: Fri Nov 8 13:09:33 1985 Date-Received: Sun, 10-Nov-85 16:54:32 EST References: <1092@mtuxo.UUCP> Reply-To: ins_apmj@jhunix.ARPA (Patrick M Juola) Organization: Johns Hopkins Univ. Computing Ctr. Lines: 52 Summary: answers to questions In article <1092@mtuxo.UUCP> 45223wc@mtuxo.UUCP (w.cambre) writes: >What's a photon? A "piece" of light, or more specifically one quantum unit of a given frequency. >What happens when two photons hit each other? They just go through each other, like waves in water. >Do photons lose energy when they bounce off things? If they are absorbed and readmitted, yes. If the thing is moving away (making a Doppler shift), yes. Otherwise, no. >Do photons lose more energy when they bounce off black things >than when they bounce off white things? No. >How about mirrors? What about them? All a mirror does is reflect coherently, rather than scatteringthe light about. >If I have a hollow sphere with a mirror coating on the inside >and a light source in it, and say the light cannot get out of the ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ You can't GET a mirror like that; it violates conservation of energy. >inside of the sphere, if I leave the light source on for a while, >will the sphere fill up with photons? Will it get full? >Will it get brighter and brighter in there? If I keep the light on >in there for 30 years then suddenly break open the sphere, will >I be blinded by all the light that explodes out of it? What would happen would be that the mirror warms up to white-hot, so it shines light away as fast as you put it in. >What's the difference between photons in a red light and photons in a >blue light. I thought red and blue light are energy in a certain >wavelength. Does a photon have a wavelength? Yes, it does. Well, actually, the energy of a photon is related to the wavelength of the light it represents. This is related to the wave-particle duality of light; light is both a stream of discrete photons and a bunch of electromagnetic waves simultaneously; the waves have a wavelength, the photon merely has energy which is equal to the speed of light times Plank's constant over the wavelength. > >Does anybody really know? > No, all this is just a theory, but it's a fairly strong one. Does anyone really know that all mammals have hair? Nothing in science is ever definite. > - Bill Cambre {ihnp4!}mtuxo!45223wc Pat Juola Johns Hopkins Univ. Dept of Maths