The article describes what lenses are, what they are used for, where they are used, and in particular about optical and contact lenses.
Development of science
At all times there were those who were interested in the true structure of the world and natural phenomena. Especially human attention was riveted to the sky and stars. The first telescopes were invented in the Middle Ages, and their appearance served as a series of astronomical discoveries. Such a thing as the development of the glass industry, and in particular lenses, also contributed to this. Around the same years, the first microscopes were invented, which were constantly improved and also helped scientists to learn the secrets of the macrocosm. So what are lenses, how are they arranged, where are they used and what are they for? We'll figure it out.
Definition
According to official terminology, a lens is a piece of transparent material with two surfaces that refract light rays. They are made of glass, plastic or other similar optical material. Also, this term can be applied to other phenomena, for example, an air lens, an underground lake lens, etc. But we will analyze the optical ones. What are lenses, we have dismantled, but how are theywork?
It's all about their surface. Simply put, one of their surfaces collects light, and the second, due to its shape, refracts it. Or vice versa. Also, both sides can participate in such a process at once: one, taking it, scatters, and the second collects it in a bundle, etc.
Everyone is probably familiar with magnifying lenses, especially boys who, in the summer, collect light, turning it into a tiny hot spot. And, by the way, an interesting fact: a similar method of making fire is mentioned in Aristophanes' play "Clouds", dating back to 424 BC. e. In the Roman Empire, the method of correcting vision with the help of a lens was also used for the first time: Emperor Nero looked at the fights of gladiators through a concave emerald. He probably suffered from myopia. So now we know what lenses are.
Classification
According to the technical principle of operation, they can be divided into two groups - scattering and collecting. The first includes those whose middle is thicker than the edges, and the second includes those whose edges are thicker than the middle. This definition refers only to their simple type.
They are also characterized by their optical power, which is measured in diopters, and focal length. But what is the focus of a lens?
In simple terms, this is the point where the light rays that have passed through the lens are collected. And the term "focal length" refers to the length from the center of the optical lens to the point of focus. This can also be explained by the example of a child's game with a magnifying glass and the sun: so that the rays of the latter gather into a hotpoint, you need to find the right distance between the light and the surface. This also manifests itself when wearing glasses - if they are too close or too far away from the eyes, the image will be blurred. So now we know what the focus of a lens is.
Applications
With the discovery of the possibility of changing the wavelength of light through lenses (enlargement of the image), humanity quickly appreciated it on merit. It all started with simple telescopes and spyglasses. And the latter for a long time were an indicator of the status of a ship's captain or a researcher, as they cost a lot of money and were often encrusted with precious stones and metals.
And later, the first microscopes made it possible to slightly open the veil of the macrocosm. True, some modern models that operate according to the probing type are almost devoid of lenses. But they allow you to build three-dimensional and raster images of small objects.
Various devices with lenses are also an integral part of the modern world: they are in the cameras of mobile phones, photo and video devices, even ordinary door eyes contain lenses. But they do not use the method of magnification, but, on the contrary, the scattering of light, thanks to which a small hole allows you to see the entire landing.
Also, when asking what optical lenses are, one cannot but mention glasses. This simple device was invented in the Middle Ages and has changed little, but it makes life much easier for people with visual impairments. Their first prototypes were used in ancient Rome, but then theywere simply flat pieces of glass with a convex or concave shape, which were rarely used, for example, for reading or for studying distant objects.
Contacts
But what are contact lenses? The principle of their operation is the same as in conventional ones, but the size is much smaller. They are made of soft plastic and are put directly on the cornea of the eye. Despite the advantages over ordinary glasses, they did not completely replace them, as the inventors predicted. Such lenses are more difficult to "put on", they need frequent care, and long-term wear tires and irritates the eyes. In addition, their service life is shorter than ordinary glasses, and the price is sometimes higher.
