It is a homework question (never been a fan of chemistry!).  I am studying aromatherapy and have been asked to draw the carbon skeleton of an isoprene unit, which I have done.  I am then asked to draw two isoprene units to form an acyclic chain as well as a cyclic chain and then a sesquiterpene and so on.  What I want to know is, what are the rules of joining isoprene units?  Am I supposed to know how they are drawn by the information given? Is there a pattern?

The other day I was opening a letter at dusk without the room lights on.  As I pulled the seal apart, I thought I saw small flashes of bluish light at the as the strands of glue broke. Has anyone heard of energy being released in the form of light when glue bonds are broken?  Might there be some phospherent chemical in the glue which is activated when the material is stressed?