1) What experiment could you quickly do to detect the difference between a real diamond and an identically shaped fake?
2) Describe the operation of a one-way mirror. Is there actually such an optical element?
3) In old spy movies diamonds are hidden in a bottle of water or vodka. Would this really work?
4) You have several concave mirrors. What quick test could you make to choose the one with the best figure? (i.e., the most constant curvature)?
5) You move a lens from your eye to arm's length away and a far scene never becomes inverted. What can you say about the focal length?