First of all excuse me if i'm posting in the wrong section or you are simply annoyed by my questions. It just happens that i love all this scientific stuff and althoughi don't always understand everything i try to. I just finished reading a very basic article about a laser operates and it talked about the excitement of a sort of particle which when struck by a photon and already excited would emit 2 photons and in the same direction that the first photon came. It also mentioned something about starting a sort of chain reaction to get all the "particles" excited. The ilustrations showed two mirrors but one of them being only partially reflective. This caused most photons to bounce back and forth exciting the particles and "creating" more photons. Some of this photons did escape the "device" trough the partially reflective mirror thus creating a laser beam. Now comes my stupid question: What if instead of a partially reflective mirror in one end i used both mirrors completely reflective?? Wouldn't it escalate whatever few photons i dumped in it infinitely???? And to help me understand even if my question is completely idiotic, i'd like to know what kind of "particles" are used that cause that effect of duplicating photons when already excited and struck a second time by another photon. Thanks for your patience and understanding with a simple man that seeks a little chunk of wisdom. Christian.