16. one point, from Lectures 14 and 16, a group question, short answer

(a) .4 What's Light Like? Light is a wave, yet it differs from other waves. Two key experiments on light as a wave were Young's double slit experiment and the Michelson/Morley experiment. Both used interference to show something about waves. Write for me the point made by each experiment (.2) and how interference was used to make the point. (.2)

(b) .3 How does Light Propagate? Maxwell actually realized that aether, a material medium, wasn't really necessary for light to propagate. Yet just as Newton with action at a distance, Maxwell couldn't see a way around having a medium for a wave, so he stuck his neck out for what turned out to be a wrong guess. What were two properties of Maxwell's aether (.2) and why were they troublesome? (.1)

(c) .3 Null Experiments What is meant by a null result from an experiment? (.1) Why is a null result useful? (.1) How does the Michelson/Morley null result illustrate this? (.1)

Revised October 8, 1997.