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A dashed horizontal line is drawn from the midpoint of the boundary between medium 1 and medium 2. Medium 1 is labeled n sub 1 and medium 2 is labeled n sub 2. An incident wave in medium 1 moves upward toward the mid of the boundary and makes angle theta sub i with the dashed line. A reflected wave in medium 1 move upwards from the mid of the boundary toward left and makes angle theta sub r with the dashed line. A transmitted wave intersects the z axis and makes angle theta sub t with the dashed line.