Wireless Optical Telecommunications

Chapter 1

Light

In the beginning God created the heavens and the earth. The earth was formless and empty, darkness was over the surface of the abyss, and the spirit of God was hovering over the waters. God said ‘Let there be light’ and there was light. God saw that the light was good: and God divided the light from the darkness. God called the light Day, and the darkness he called Night. And there was evening and there was morning, it was the first day.

“Fiat Lux — Let there be light”Old Testament,The Pentateuch — Genesis 1,Chapter 1

Light has long fascinated man, exalted depictions by painters or praise from writers, with many areas of study for scientists and scholars. Figure 1.1 represents, for example, Lady Taperet (22nd Dynasty, 10th or 9th Century BC) praying to the sun god Ra-Horakhty. The symbolism of light provides an almost unlimited field for celebration of all kinds in all civilizations, past and present.

For centuries, the only known radiation was light. The first written analysis of light seems to date from Greek and Latin civilizations. For the Greeks, Euclid (325–265 BC) and Ptolemy (90–168 BC), the light is emitted from our eye and is the vector of an object image. On the other hand, Epicurus (341–270 BC) and the Latin poet Lucretius (98–55 BC) thought that the bright objects sent little pictures of themselves into space, referred to as “simulacras”. These simulacras were entering our eyes so we could “see” these objects. This latter theory called “corpuscular ...