  pick up a set of lecture notes on the fundamentals of optics: "optics is a discipline that appears to have found the secret of eternal life... lasers, a solution without a problem in my youth, are now (among other things) making extraordinary advances in basic physics. " spent the morning on physics questions that i will never get to see in an O Level exam. that is damned stupid. but as both misters foo and tay will say, it's good practise. why prepare for something that is two years ahead when you can prepare four years ahead? forethought! like john cleese in the "self defence against fresh fruit" sketch, you must have a sixteen tonne weight ready at all times. on to more important things. "sketch" or "skit"? if i'm not wrong, a sketch usually has only one scene. a skit is more general but most probably implies a work of an amateur. but that's only my interpretation, i am probably wrong in any case. okay. bye. 
