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A wedge-shaped film of air is made by placing a small slip of paper between the edges of two flat glass plates. Light that has a wavelength of 600 nm is incident normally on the glass plates, and interference fringes are observed by reflection. (a) Is the first fringe near the point of contact of the plates dark or bright? Why? (b) If there are five dark fringes per centimetre, what is the angle of the wedge