The line of incidence.
When the ball bounds back, what is its path called?
The line of reflection.
What is the angle at which a ball strikes the wall called?
The angle of incidence.
What is the angle at which the ball rebounds called?
The angle of reflection.
When a ray of light falls upon a looking-glass, what is the path through which it goes called?
The line of incidence.
When the ray is reflected, what is its path called?