2. A Fizeau interferometer is used to compare a convex spherical surface (100 m radius of curvature) against a flat surface. The flat surface is 100 mm in diameter and the spherical surface is 50 mm in diameter. The wavelength of illumination is 500 nm. The two surfaces touch at the center. The interferogram is viewed in reflection. a. Is the central spot bright or dark? b. How many bright circular fringes are seen? c. If the two surfaces are moved apart (without introducing tilt) will the circular fringes expand from the center or contract towards the center? 2. A Fizeau interferometer is used to compare a convex spherical surface (100 m radius of curvature) against a flat surface. The flat surface is 100 mm in diameter and the spherical surface is 50 mm in diameter. The wavelength of illumination is 500 nm. The two surfaces touch at the center. The interferogram is viewed in reflection. a. Is the central spot bright or dark? b. How many bright circular fringes are seen? c. If the two surfaces are moved apart (without introducing tilt) will the circular fringes expand from the center or contract towards the center