reflections

Reflection, in physics, phenomenon of wave motion, in which a wave is returned
after impinging on a surface. When energy, such as light or sound, traveling
from one medium encounters a different medium, part of the energy usually
passes on while part is reflected. Regular reflection (in which the direction
of the reflected wave front is sharply delineated) is governed by the law that
both the incident, or striking, rays and the reflected rays travel in directions
making equal angles with the normal, a line perpendicular to the reflecting
surface at the point of incidence; and that the rays lie in the same plane as
the normal. These angles are called the angle of incidence and the angle of reflection.
Rough surfaces reflect in many directions, and such reflection is called diffuse.

Istvan Hilgert
www.jointsoftime.org