I CAN SEE THE WORLD........

 An object which can show the image clearly and zoomed as much we can see is called lens. Today by today, the people use the lens for see clearly. The lens in our eye is also equal to the lens that made by us. But, some of the humans eye ball get elongated, which they can't able to see clearly......

THE LENSES......

A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while compound lens consists of several simple lenses , usually arranged along a common axis. Lenses are made from materials such as glass or plastic, and are ground and polished or molded to a desired shape. A lens can focus light to form an image, unlike a prism, which refracts light without focusing. Devices that similarly focus or disperse waves and radiation other than visible light are also called lenses, such as microwave lenses, electron lenses, acoustic lenses, or explosive lenses.

The Lens When was it invented, the little piece of glass that would change the world? No one knows for sure. By Peter Hennig In Ancient China, Greece, and Rome, they probably used 'magnifying-stones' of polished rock crystal, but it was not until about 1000 that the principles of the lens were properly described by an Arabic physicist, Ibn el-Haitam. His was not only the first correct account of how light is refracted by a lens, but also of how the eye functions in principle.By the end of the sixteenth century it was known how a microscope worked. The basic model consisted of two positive lenses at a certain distance from each other, the one in front being small and strongly magnifying. It is a design that is not difficult to come up with if you sit experimenting with different lenses. Nor was the microscope seen as having any great significance to begin with. It was a curiosity that might entertain for a while, a 'flea-glass' that could turn the tiniest insect into terrible monster.

Even the telescope may have been discovered more or less by chance, although one version of the story credits its inventor with a more deliberate approach. It is said that in 1608 a Dutch lens maker, Hans Lippershey, received an order for two lenses. One was to be slightly larger and weakly convergent, the other to be smaller and concave, in other words a diverging lens. When the customer came to collect them, he held the lenses at arms' length from each other, smiled happily, paid, and left.
Lippershey was perplexed, and found no peace until he had cut two more lenses so that he could see what was going on for himself. To his amazement he found that a distant church tower appeared so close that he could see the weather vane quite clearly. News of the invention spread quickly, and only a short time later in Italy, Galileo Galilei began his pioneering study of celestial bodies.


The human eye is quite weak in comparison with the eyesight of many predators. Yet we can see more than any other creature because we have supplemented our eyes with extra lenses.
During the seventeenth century, the lens started a formidable revolution in our ability to explore our surroundings and increase our knowledge, and gradually made it possible to alter our circumstances in a positive way.
The new optical instruments brought rapid improvements in navigation, with dramatic results for trade and shipping. Telescopes scanned the heavens - and the old world view died. Microscopes sought out the smallest details - and a whole new world was revealed that we had had no inkling of before.
This was a completely new branch of the tree of knowledge, and it changed our lives in many ways. New instruments that provided new information were fundamentally to change our way of looking at the world, but the lens also contributed change in less dramatic ways.
When it comes to gathering information and assembling knowledge at an individual level, the longer one can continue the better the results. Until the seventeenth century, most specialists ceased their active working life in their forties or fifties when deteriorating eyesight made any detailed work impossible. Once simple spectacles came within their means it meant there was something of a trade revolution, because they could stay active for another fifteen to twenty years. This era marks the beginning of the rapidly accelerating accumulation of knowledge that was to become the technical basis of the industrial revolution in the eighteenth century.


Even the ancients knew that you could project a picture onto a wall when light shone through a little hole into a darkened room. Such large-scale pinhole cameras were in use in the fifteenth century. Sitting inside one, you could draw from the surprisingly bright images. When in the 1550s the hole was replaced with a lens, the brightness and definition increased so much that it became much more useful. In the seventeenth century portable camera obscura were constructed that employed the reflex mirror principle.
Of course people dreamed of being able to capture the 'pictures from nature' that the lens showed so beautifully, and there was an eager search for materials that reacted to light and could be used to record the images.

The discovery of the century
It is usual to date the birth of photography to the introduction of the Daguerreotype in 1839, but it could be said to have been essentially a reinvention - most of the technique was already known. The lens was known, the camera was known, and the reaction of silver salts when exposed to light had been known for a hundred years. What made it new was that everything was brought together, while the problem of making the silver salts sufficiently sensitive to light was solved, and a method was found of fixing the pictures so that they did not darken further when exposed to more light. If you tried to patent this under today's rules, it would be a matter of arguing for a second class patent, or a patent on a new application of an already known technique. Still, contemporaries saw photography as the invention of the century, a reasonable view considering the role photography would come to play.


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