Light may be regarded as the best known and most fascinating part of the electromagnetic spectrum. While all radiation is defined as the emission or transport of energy by particles or waves, transmission of information [1] is perhaps the most important aspect of electromagnetic radiation, of which visible light presents only a very narrow band [2] . Like all radiation, light shows properties of particles and waves. On this page, the focus is generally on the wave nature which can be vividly demonstrated by the Huygens-Fresnel principle [3] .
In addition to visible light, space carries electromagnetic radiation of different wavelengths transmitting huge amounts of information (e.g., wireless telecommunication, radio, TV, and Internet signals, as well as faint signals from astronomical objects, detectable only with sophisticated telescopes).
Visible light’s wavelength band (0.4 - 0.8 micrometer) is extremely narrow when compared to the total spectrum of electromagnetic radiation.
The principle basically says that any point touched by a wavefront becomes the source of a new wave. Accordingly, we can imagine our sunlit surrounding as an ultra-high-resolution 3D-picture composed of an infinite number of tiny dots (pixels) that emit electromagnetic radiation carrying information about color (blend of different wavelengths), intensity (wave amplitude) and shine (polarization), all sensed in miraculous ways by our eyes and processed in the brain.