1. n. 
Generally, the return or rebound of particles or energy from the interface between two media. There are two laws of reflection, which state (1) that incident rays, reflected rays and the normal to the reflecting interface at the point of incidence are coplanar, and (2) that the angle of incidence is equal to the angle of reflection. In geophysics, reflection refers to the seismic energy or signal that returns from an interface of contrasting acoustic impedance, known as a reflector, according to Snell's law. Reflection seismic surveys are useful for mapping geologic structures in the subsurface, interpreting sedimentary environments and evaluating hydrocarbon accumulations that might occur as amplitude anomalies. Reflection surveys are complicated by the variation of velocity as well as the various types of wave energy that are propagated within the Earth. In electromagnetics, variation in electrical properties produces reflections.
See: acoustic transparency, amplitude anomaly, arrival, attenuation, autotrack, complex trace analysis, converted wave, critical reflection, deep seismic sounding, diffraction, drill-noise vertical seismic profile, electromagnetic method, Fermat's principle, footprint, primary reflection, raypath, reflection coefficient, reflector, refraction, seismic-while-drilling vertical seismic profile, Snell's law