Lenses
This task is all about lenses and how they refract light. It can be done entirely by research online.
a) What is a plano-convex lens? What is it useful for?
b) What is a Fresnel lens? Why is this very commonly used in stage lighting?
c) What is a plano-concave lense? Why are these not so often found in stage lighting?
Include a ray diagram for each type to illustrate your explanations. If you cannot find enough detail about plano-convex or plano-concave lenses, normal convex (also called bi-convex or double convex) and concave (also called bi-concave or double concave) lenses will do – but note that these are not found in stage lamps so you will have to explain how the idea applies to stage lighting).