1. The problem statement, all variables and given/known data These are more-so explanation based and there is no math involved. 1) How come someone with "normal vision" does not require glasses? 2) Why does a far sighted person require glasses with a positive focal length? 3) Why does a near sighted person require glasses with a negative focal length? It's bad enough that we have not covered the chapters dealing with optics in lecture yet, so some brief clarification would be greatly appreciated. Thank you!