Two Flat Planes of Glass Are Laid on Top of One

Multiple Choice

Two flat planes of glass are laid on top of one another.The upper plane is slightly raised due to the insertion of a thin piece of paper at one end and an air wedge is thus formed.Light of wavelength 500 nm is normally incident on the glass from above and interference fringes are observed by reflection with 2.5 fringes per cm.Calculate the angle of the wedge.

A) 6.3 $\times$ 10^-5 deg
B) 1.8 $\times$ 10^-3 deg
C) 4.0 $\times$ 10^-4 deg
D) 3.6 $\times$ 10^-3 deg
E) 5.7 $\times$ 10^-4 deg