Light

Most early civilizations worshipped a sun god in some form, and even the Judeo-Christian bible depicts God's first act of creation to be producing light. "And God said, 'Let there be light,' and there was light." (Genesis 1:3)

For Aristotle (384 BC - 322 BC), the key to light was in transparent bodies as the presence of fire or something resembling fire. Much later, Rene Descartes (1596 - 1650) an early renaissance scientist described light as a disturbance transmitted through ether. Though many of Descartes theories were inaccurate, he was the first to theorize that different colors of the spectrum were associated with different periodic motions of some kind.

Corpuscular Theory

Issac Newton (1642 - 1727) is one of the earliest optical scientists. He researched light and published a book called "Opticks" in 1705. Newton incorrectly noticed that light, unlike other types of waves transmitted as a disturbance, did not seem to bend around objects the way other waves did and he therefore concluded that light was not a wave, but a corpuscle or small particle which traveled only in a straight line. Light, however, is a wave, and is subject to diffraction, though much less pronounced than with other waves like water.

A Jesuit priest, Fr. Francesco Maria Grimaldi (1613 - 1663) was the first to observe the bending of light around an obstacle. He called it diffraction. Newton, however, thought Grimaldi's results were due to refraction.

Unfortunately, due of the authority and backing of Newton, the corpuscular theory was more generally accepted by scientists throughout the 1700's. That changed as a result of the research of two men, Thomas Young (1773 - 1829) and Augustine Fresnel (1788 - 1827). Young, trained as a doctor and making contributions in medicine, linguistics, mechanics and optics, was the first person to conclusively demonstrate the wave property of interference with light using his Double Slit Experiment, which lead credence to the wave theory.

It is now known that light, though a transverse wave, has many properties in common with sound, such as, wavelength, (color) intensity or amplitude, superposition and interference, refraction, Doppler effect, and a distinct speed. The main difference between light and sound is that light is an electromagnetic transverse wave like a radio wave that vibrates at a very much higher frequency.

Because light is a transverse wave rather than a longitudinal wave, it has polarization effects.

Color

The wavelength, or vibrational rate, is experienced by our eyes as color.