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 546nm light from a mercury-vapor lamp. Interference fringes are formed, with 12.0 fringes/centimeter.
A- Find the angle of the wedge.
Please show how you obtained the answer.