Willoughby Smith
Encyclopedia
Willoughby Smith was an English electrical engineer who discovered the photoconductivity
of the element selenium
. This discovery led to the invention of photoelectric cells, including those used in the earliest television systems.
In 1848, he began working for the Gutta Percha Company, London where he developed iron and copper wires insulated with gutta-percha
to be used for telegraph wires. In 1849, Smith superintended the manufacture and laying of 30 miles of underwater telegraph wire from Dover
to Calais
. He worked closely with Charles Wheatstone
who had designed the machinery for making and laying the cable.
The project was a success and over the following decades, Smith and the company he worked for were involved with many other underwater telegraph cable projects.
In 1873. Smith developed a method for continually testing an underwater cable as it was being laid. For his test circuit, he needed a semi-conducting material with a high resistance and selected selenium rods for this purpose.
The selenium seemed to do the job properly, except in actual use, the device gave inconsistent results. Upon investigation, it was discovered that the conductivity of the selenium rods decreased significantly when exposed to strong light.
Smith described the "Effect of Light on Selenium during the passage of an Electric Current" in an article that was published in the 20 February 1873 issue of Nature.
Photoconductivity
Photoconductivity is an optical and electrical phenomenon in which a material becomes more electrically conductive due to the absorption of electromagnetic radiation such as visible light, ultraviolet light, infrared light, or gamma radiation....
of the element selenium
Selenium
Selenium is a chemical element with atomic number 34, chemical symbol Se, and an atomic mass of 78.96. It is a nonmetal, whose properties are intermediate between those of adjacent chalcogen elements sulfur and tellurium...
. This discovery led to the invention of photoelectric cells, including those used in the earliest television systems.
In 1848, he began working for the Gutta Percha Company, London where he developed iron and copper wires insulated with gutta-percha
Gutta-percha
Gutta-percha is a genus of tropical trees native to Southeast Asia and northern Australasia, from Taiwan south to the Malay Peninsula and east to the Solomon Islands. The same term is used to refer to an inelastic natural latex produced from the sap of these trees, particularly from the species...
to be used for telegraph wires. In 1849, Smith superintended the manufacture and laying of 30 miles of underwater telegraph wire from Dover
Dover
Dover is a town and major ferry port in the home county of Kent, in South East England. It faces France across the narrowest part of the English Channel, and lies south-east of Canterbury; east of Kent's administrative capital Maidstone; and north-east along the coastline from Dungeness and Hastings...
to Calais
Calais
Calais is a town in Northern France in the department of Pas-de-Calais, of which it is a sub-prefecture. Although Calais is by far the largest city in Pas-de-Calais, the department's capital is its third-largest city of Arras....
. He worked closely with Charles Wheatstone
Charles Wheatstone
Sir Charles Wheatstone FRS , was an English scientist and inventor of many scientific breakthroughs of the Victorian era, including the English concertina, the stereoscope , and the Playfair cipher...
who had designed the machinery for making and laying the cable.
The project was a success and over the following decades, Smith and the company he worked for were involved with many other underwater telegraph cable projects.
In 1873. Smith developed a method for continually testing an underwater cable as it was being laid. For his test circuit, he needed a semi-conducting material with a high resistance and selected selenium rods for this purpose.
The selenium seemed to do the job properly, except in actual use, the device gave inconsistent results. Upon investigation, it was discovered that the conductivity of the selenium rods decreased significantly when exposed to strong light.
Smith described the "Effect of Light on Selenium during the passage of an Electric Current" in an article that was published in the 20 February 1873 issue of Nature.