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 [Broken] [Broken] [Broken] [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.