PHGN462 - Electromagnetic Waves and Optical Physics
Fall 2009
Assignment 12
Due Monday, Nov. 30
1. Read Ghatak Ch. 15.1-5, 8.
2. Ghatak 15.1: A glass plate of refractive index 1.6 is in contact with another glass plate of refractive index 1.8 along a line such that a wedge of 0.5 degrees is formed. Light of wavelength 500 nm is incident vertically on the wedge, and the film is viewed from the top. a. Calculate the fringe spacing (with air between the plates). b. The whole apparatus is immersed in an oil of refractive index 1.7. What will be the qualitative difference in the fringe pattern and what will be the new fringe width
3. Ghatak 15.2: Two plane glass plates are placed on top of each other, and on one side a cardboard is introduced to form a thin wedge of air. A beam of light of wavelength
600 nm is incident normally on the top plate and 100 interference fringes per cm are observed. What is the angle of the wedge?
4. Ghatak 15.3: Consider a nonreflecting film of refractive index 1.38 that is 900 mm thick. a. Calculate the wavelengths in the visible part of the spectrum for which the coating will be nonreflecting. b. Repeat the calculation for a film five times thicker and identify the wavelengths where both films will be nonreflecting. Why is the thinner film more suitable?