1. The problem statement, all variables and given/known data Well, this is the first time I posted in English, so please excuse my expression. The question is a kind of game. I have 50 pothographies about Optics (phenomens, experiments, people,...), but don't worry I only need help for 4. I have find de solution for 44 and there is 2 that I have some clue. So, somebody can help me with this 4. Remenber, all them talk about optics (phenomen, experiment, instrument...). A lot of thanks 2. Relevant equations http://img99.imageshack.us/img99/9190/foto3tc1.jpg [Broken] http://img184.imageshack.us/img184/3599/foto4gk6.jpg [Broken] http://img187.imageshack.us/img187/8319/foto1nb4.jpg [Broken] http://img183.imageshack.us/img183/8291/foto2dm1.jpg [Broken] 3. The attempt at a solution The thrid one is maybe a ion trap, and the last one is obviously something huge. A lot of thanks again.