See reflection loss.

The abrupt change in direction of a wave front at an interface between two dissimilar media so that the wave front returns into the medium from which it originated.
Note 1: Reflection may be specular (i.e., mirror-like) or diffuse (i.e., not retaining the image, only the energy) according to the nature of the interface.
Note 2: Depending on the nature… (Read More →)

1. The ratio of the amplitude of the reflected wave and the amplitude of the incident wave.
2. At a discontinuity in a transmission line, the complex ratio of the electric field strength of the reflected wave to that of the incident wave.
Note 1: The reflection coefficient may also be established using other field or circuit quantities.
Note 2:… (Read More →)

1. At a discontinuity or impedance mismatch, e.g., in a transmission line, the ratio of the incident power to the reflected power.
Note 1: Reflection loss is usually expressed in dB.
Note 2: The reflection loss, Lr, is given by where Z1 and Z2 are the respective impedances, and the vertical bars designate absolute magnitude.
2. In an optical fiber,… (Read More →)

An antenna, such as a billboard antenna, in which the driven elements are situated at a predetermined distance from a surface designed to reflect the signal in a desired direction.
Note: Reflective array antennas (a) usually have many driven elements working in conjunction with an electrically large reflecting surface to produce a unidirectional beam, (b) may be used to increase… (Read More →)

The reflectance at the surface of a material so thick that the reflectance does not change with increasing thickness, i.e., the intrinsic reflectance of the surface, irrespective of other parameters such as the reflectance of the rear surface.
Note: The term "reflectivity" is no longer in common use. See reflectance.

1. In an rf antenna, one or more conducting elements or surfaces that reflect incident radiant energy.
Note: A reflector may consist of a large surface, as in a dish antenna, or a linear element, as in a Yagi antenna.
2. See mail reflector.

1. A ray that undergoes a change of velocity, or in the general case, both velocity and direction, as a result of interaction with the material medium in which it travels.
2. In an optical fiber, a ray that is refracted from the core into the cladding. Specifically a ray having direction such that where r is the radial distance… (Read More →)

Retardation, and--in the general case--redirection, of a wavefront passing through (a) a boundary between two dissimilar media or (b) a medium having a refractive index that is a continuous function of position, e.g., a graded-index optical fiber.
Note: For two media of different refractive indices, the angle of refraction is closely approximated by Snell's Law.

Synonym refractive index profile.