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The medium 1 is labeled, eta sub 1, the reflected wave rays move in the slanting in the North East from the mid of the boundary. The horizontal dashed line is drawn crossing the midpoint of the boundary in both the mediums. The angle theta sub r can be measured from the dashed line to the reflected wave. The incident waves from bottom left moves in the slanting from the South East toward the mid of the boundary. The angle theta sub I is measured from boundary to incident waves. The medium 2 is labeled, n sub 2, and transmitted wave rays move in the North West from the mid of the boundary line. Angle theta sub t can be measured from transmitted wave to dashed line.