A lens is any entity that has the ability to deflect rays of light through it. Likewise, lenses are transparent objects (made mainly of glass) made up of two surfaces, one of which is curved and the other is flat.
The word lens derives from the Latin lens or lentis, which means “lentil”, it has been baptized with this name due to its similarity (in its shape) with the well-known legume. Likewise, this word is of ambiguous gender, since it is usually used in feminine to refer to optical glass, while when used in masculine it refers (in some countries) to glasses or reading glasses or sun protection.
Lenses began to appear in the early 13th century, when manufacturers created small glass discs that could be mounted on a frame, with the aim of increasing the size of things and protecting the human eye from intense light. It was since then that the first reading glasses or book glasses were created.
Depending on the shape of the lenses, they can be convergent or divergent. Converging lenses are characterized by being thicker in the center and narrower at the edges. They get their name because the light rays come together or converge at a certain point called the image focus. These in turn can be; biconvex, plano-convex or concave-convex.
For their part, divergent lenses become thicker at the edges, while becoming increasingly narrower as the center is reached. They get their name, because they separate or diverge all the rays of light parallel to the main axis that pass through them and their image focus is on the left, while the converging ones have it on their right side. The diverging lens may be; biconcave, plano-concave or convex-concave.
Currently there are so-called artificial lenses, since they are built with non-homogeneous artificial materials, causing their behavior to exhibit lower refractive indices, that is, a divergent artificial lens can become biconvex. This type of lens becomes very useful in microwaves thanks to its properties.
