Final answer:
The angle of incidence refers to the angle between the chord line of a blade and the plane of rotation in a rotor system, crucial in physics subjects, particularly optics and aerodynamics.
Step-by-step explanation:
The angle of incidence is between the chord line of each blade and the rotor system's plane of rotation. In physics, especially when discussing optics or aerodynamics, the angle of incidence is a measure of deviation of something from 'straight on,' for instance, the angle at which the wind hits an airplane wing or blade. The chord line is the straight line connecting the leading and trailing edges of an airfoil, such as a wind turbine blade, while the plane of rotation would be an imaginary flat surface that represents the circular path the blades take as they rotate around the rotor hub.