An overview of Thomas Young's contributions to the fields of vision and light

Thomas Young was best known as a physician and physicist with a strong interest in sensory perception however he was a man of many interests.  Not only was he a gifted scientist and physician he was also fluent in several languages and studied Egyptology. In 1814 he began to study the Rosetta stone and went on to help translate the language of the ancient Egyptians.

Young made his first notable discovery while still in medical school when he found that the lens of the eye changes shape as it focuses on objects at varies distances. He went on to discover the cause of astigmatism in 1801.

Thomas Young and Hermann Ludwig Ferdinand von Helmholtz developed what would become known as the Young-Helmholtz trichromatic theory.  This theory speculated that there were three types of cones in the human retina, which receive color stimulus and transmit it to the brain.  According to their theory each of the three types of cones are sensitive to one of three colors, red, green, or blue. Today our best understanding of the cones is that there are between 6 and 7 million with 64% being sensitive to red, 32% to green and 2% to blue.

Young began his experiments into the phenomenon known as interference in 1801 and this led to his wave theory of light. By splitting a beam of light from a single source and then recombining it he noticed that the light produced dark and light fringes. He concluded that the fringes were the result of the light acting as a wave with the peaks and troughs reinforcing or cancelling out one another.

English scientist did not immediately accept Young’s theory because it defied Newton’s theory of light.  According to Newton’s theory, which was published in 1704, light was made up of particles emitted by their source. Young’s theory began to be more widely accepted after he worked with French physicists Augustin Fresnel and Francois Arago. Fresnel had also experimented with the laws of interference although he achieved little notoriety for his work in optics. He is perhaps best known for developing the compound lens that replaced mirrored lenses in lighthouses. Arago made major contributions to the study of electromagnetism and the phenomenon of magnetic rotation. Along with French physicist Augustin-Jean Fresnel he discovered the principles governing the polarization of light, a key discovery in establishing the theory of light as a wave.

Young is credited with giving the word energy its scientific significance; he also worked on elasticity, surface tension of liquids and measuring the size of molecules.