Deciphering Light


Ancient Greeks developed some theories that explained what light is, making it possible for scientists to decipher it. Muslim scientist Alhazen had the most prominent contribution to the study of light and the mechanism of vision; this is evident in his work The Book of Optics, which was translated into Latin five times. Alhazen’s theory is credited for the invention of the camera and the foundation of optics science.

Scientific research of light halted until the 17th century, when Isaac Newton resumed the journey to unravel the secrets of light, introducing the Particle Theory, which defines light as a bundle of particles and atoms that moves in straight lines. Newton strongly defended his theory, which helped us learn that light refracts into several colors later known as rainbow. It also showed that visible light ranges between 400 and 700 nanometer, spanning between the longer infrared light waves and the shorter ultraviolet light waves. The journey did not end with Newton; Dutch scientist, Christiaan Huygens, developed another theory of light, the Wave Theory, in which he proved that light moves in waves similar to water waves.

Since then, a fierce battle between the proponents of Newton’s Particle Theory and the supporters of Huygens’ Wave Theory lasted for around one-hundred years. The battle only ended when the famous German scientist, Einstein, conducted a new study of light. He proved that light behaves like particles that he named photons, which are launched, accelerated, and weakened according to the simulation of atomic electrons, and also like waves that interfere at the top and the bottom, affecting the light’s intensity. A new theory of light known as the Wave-Particle Duality Theory emerged; it was the PhD dissertation of scientist Louis de Broglie. These theories paved the way for scientists to study light refraction and reflection, as well as the optical polarization theory that helped eliminate the annoying light reflection in sunglasses and camera filters.

The sources of light are diverse; the most famous are thermal ones, such as sunlight, which travels to Earth in 8:20 light minutes. Other sources include chemoluminescence; chemical substances emitting light, bioluminescence; living organisms emitting light such as some fish and trees, and phosphorescence; emission of the phosphoric light from radiated materials.

Scientists estimated light’s wavelength to be 0.000001 m. Italian scientist Galileo, Danish scientist Rømer, Hippolyte Fizeau, Léon Foucault, and Albert A. Michelson, all exerted remarkable efforts to measure the speed of light through different experiments; it was finally determined to be 299.792.458 m/s.

The unraveling of light has indeed been a lengthy journey, which started back in the Middle Ages and has not come to an end yet.


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SCIplanet is a bilingual edutainment science magazine published by the Bibliotheca Alexandrina Planetarium Science Center and developed by the Cultural Outreach Publications Unit ...
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