Light and Color

Questions for Week One—Interference

 

Write well-reasoned verbal answers to these questions. You should be able to find the base for your answer in the week’s readings, but the questions are not directly answered there. You have to think them out, using the facts and concepts from the reading. Calculations are not necessary, though if you find it useful, include them by all means. Make sure your prose is clear and complete. One or two paragraphs should be enough for each question.

 

(1) Use wave superposition ideas to argue that there should be a bright spot at the very center of the shadow of a circular obstacle, such as a disk or ball bearing placed in a beam of monochromatic (single-wavelength) light. (Such a spot actually exists: predicted by the French physicist Poisson, it is called Poisson's spot. So stick to it, and you may get a spot named after you.)

 

(2) Why would antireflection coatings be specially needed in complex lens systems, as the reading claims?

 

(3) Why does white light not produce fringes in a Michelson interferometer, but only "light restricted in wavelength" does?