Significant Advances Made During the 12th to 16th Centuries
One of the most significant advances duri ng the 12th to 16th were the discoveries in the field of optics.The earliest written records of lenses dates to an ancient Greek play, mentioning a burning-glass “(a biconvex lens used to focus the sun's rays to produce fire)”.1 The writings of Pliny the Elder also show that burning-glasses were known to the Roman Empire, and mentions what is possibly the first use of a corrective lens.2
“Convex lenses produce an image of an object at infinity at their focus; if the sun is imaged, all the infrared energy incident on the lens is concentrated on the small image. A large lens will concentrate enough energy to heat an inflammable object on which the image falls to the burning point. Such lenses, which do not need to be even approximately optically accurate, have been used as burning-glasses for hundreds of years”.3
“A modern application is the use of relatively large lenses to concentrate solar energy on relatively small photovoltaic cells, harvesting more energy without the need to use larger, more expensive, cells.” 3 This modern solar energy may be the salvation of the future, as an alternative to oil and other unrenewable resources. It is somewhat amazing to me that in all these hundreds of years, we have not taken advantage of this next to free source of heat and energy on a massive scale.
However it was not until the 13th century that Roger Bacon, the father of experimental science, (the modern scientific method), first wrote about the magnifying properties of lenses. One of the first things that was noticed was how a crystal vase which was round ed on the bottom and filled with water had a magnifying effect on whatever was seen through it. “Eyeglasses appeared first in Florence about 1280 and their use spread rapidly. (Their invention is traditionally assigned to Alessandro di Spina)”.2
Lenses are used for the correction of visual problems such as myopia,...