Here is the problem which I am struggling on, please help me!
Problem: Two rectangular pieces of plane glass are laid one upon the other on a table. A thin strip of paper is placed between them at one edge, so that a very thin wedge of air is formed. The plates are illuminated at normal incidence by 541nm light from a mercury-vapor lamp. Interference fringes are formed, with 18.0 fringes/centimeter, find the angle of the wedge.
Rework your solution from the beginning and check each step carefully.