any disturbance that transmits energy through matter or empty space.

the transfer of energy as electromagnetic waves.

The range of wavelengths or frequencies over which electromagnetic radiation extends.

 the bouncing back of a ray of light, sound, or heat when the ray hits a surface that it does not go through.

The process in which energy of light radiation is transferred to a medium through which it is passing.

  The process in which energy is removed from a beam of light radiation and reemitted without appreciable change in wavelength.

Refraction

 the bending of a wave as the wave passes between two substances in which the speed of the wave differs.

The change in wave propagation as affected by the presence of obstacles (eg, sea walls or islands).