Reflection

Reflection is the return of a wave from a surface or boundary into the medium it came from. Its direction and strength depend on the boundary and the wave’s properties.

Law of reflection: A geometric rule stating that the angle of reflection equals the angle of incidence, measured from the surface normal. It predicts the reflected direction for a wave meeting a smooth boundary.
Wave: A disturbance that propagates through space or a medium, transporting energy and sometimes momentum. Reflection is one possible outcome when a propagating disturbance reaches a boundary.
Mirror: A surface designed to reflect light in a controlled direction or pattern. Mirrors use specular reflection to form images and redirect optical paths.
Refraction: The change in a wave’s direction as it enters a medium where its propagation speed differs. At an interface, refraction redirects the transmitted portion while reflection returns another portion.
Fresnel equations: Equations that calculate how much light is reflected or transmitted at an interface between materials. They quantify reflection from a boundary using refractive indices and polarization.
Boundary condition: A constraint on physical quantities at a surface or interface that helps determine a system’s behavior. Continuity or discontinuity at the boundary sets the reflected wave.
Fiber-optic communication: The transmission of information as light pulses through optical fibers. Total internal reflection confines light within the fiber core.
Transmission coefficient: A measure of the fraction of incident wave amplitude or energy transmitted through a boundary. Transmission accounts for energy that does not return as a reflected wave.
Impedance mismatch: A difference in wave impedance between adjoining media that causes part of an incident wave to reflect. The size of the mismatch governs reflection strength in many wave systems.
Wavelength: The distance between successive corresponding points on a periodic wave. Wavelength relative to surface roughness helps determine whether reflection is specular.

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