THE MENLO ROUNDTABLE
Figure 2: Diagramming the lengths and angles 
e following refers to Figure 2.
Finding length c-b:
1. With no water in the prism, mark on the sheet of paper the point where the beam enters the triangular prism (Point d).
en put a mark where the point exits the prism (Point e).
e line between d and e is the path of the undiverted beam.
Mark where the undiverted laser lands on the wall.