Chapter 2: Optics

The study of the behavior and qualities of light, including its interactions with matter and the design of instruments that use or detect light, is the focus of the field of physics known as optics. In most cases, the behavior of visible, ultraviolet, and infrared light is described by the profession of optics. Light is a sort of electromagnetic radiation, and other types of electromagnetic radiation, including as X-rays, microwaves, and radio waves, exhibit properties that are comparable to those of light.

It is possible to account for the majority of optical phenomena by employing the traditional electromagnetic description of light; yet, it is frequently challenging to put these comprehensive electromagnetic explanations of light into practice. The practice of practical optics typically involves the use of simplified models. Light is viewed as a collection of rays that move in straight lines and bend when they pass through or reflect from surfaces in geometric optics, which is the most frequent of these types of optics. A more comprehensive model of light is known as physical optics. This model takes into consideration wave phenomena like diffraction and interference, which are not accounted for in geometric optics. In the course of human history, the ray-based model of light was initially developed, and then the wave model of light was produced after that. It was during the 19th century that advancements in electromagnetic theory led to the realization that light waves were, in fact, electromagnetic radiation.

Certain occurrences are dependent on the fact that light possesses both wave-like and particle-like qualities. The field of quantum mechanics is required in order to explain these phenomena. Light is modeled as a collection of particles known as "photons" when the particle-like qualities of light are taken into consideration. The field of quantum optics is concerned with the concept of applying quantum mechanics to optical systems.

The study of optical science is relevant to and researched in a wide variety of related topics, such as astronomy, numerous engineering sectors, photography, and medicine (especially ophthalmology and optometry, in which it is referred to as physiological optics). Mirrors, lenses, telescopes, microscopes, lasers, and fiber optics are just few of the examples of practical applications of optics that may be found in a wide range of technology and common things.

The invention of lenses by ancient Egyptians and Mesopotamians is considered to be the beginning of the field of optics. According to the Archaeological Museum of Heraclion in Greece, the first known lenses were manufactured from polished crystal, most commonly quartz, and date back to the year 2000 BC. Lenses from Rhodes date back to approximately 700 BC, as do lenses from Assyria, such as the Nimrud lens example. In order to create lenses, the ancient Greeks and Romans filled glass spheres with water. After these practical achievements, ancient Greek and Indian philosophers developed theories of light and vision, and the Greco-Roman culture contributed to the development of geometrical optics. Both of these developments occurred after these practical developments. The origin of the word optics can be traced back to the ancient Greek word ?pt???, which means "appearance" or "look."

The intromission theory and the emission theory were two rival theories that emerged from Greek philosophy on optics. Both of these theories attempted to explain how vision functioned. From the perspective of the intromission approach, vision was thought to originate from things that emitted copies of themselves, which were referred to as eidola, and were then collected by the eye. This hypothesis appears to have some contact with contemporary theories of what vision actually is, despite the fact that it was propagated by a large number of people, including Democritus, Epicurus, and Aristotle, as well as their followers. However, it remained little more than speculation and lacked any experimental base.

Plato is credited with being the first person to enunciate the emission theory, which proposes that the eyes project rays that are responsible for visual perception. The parity reversal of mirrors in Timaeus was another topic that he discussed. One hundred years later, in the fourth or third century B.C., Euclid authored a treatise called Optics. In it, he established a connection between vision and geometry, thereby establishing the field of geometrical optics. In his study, he based it on Plato's emission theory, in which he defined the mathematical principles of perspective and qualitatively characterized the effects of refraction. However, he questioned the possibility that a beam of light from the eye could instantly light up the stars every time someone could blink their eye. The notion of the shortest pathway of light was articulated by Euclid, who also took into consideration the many reflections that occur on spherical and flat mirrors.

A theory of vision known as extramission-intromission was proposed by Ptolemy in his work Optics. According to this theory, the rays (or flux) coming from the eye formed a cone, with the vertex being located within the eye and the base defining the visual field. Because of their sensitivity, the rays were able to communicate with the observer's mind and provide information regarding the distance between surfaces and their orientation. A significant portion of Euclid's work was summarized by him, and he proceeded to provide a method for measuring the angle of refraction. However, he failed to recognize the empirical connection that exists between the angle of refraction and the angle of incidence. Over the course of the first and second centuries after the common era, Plutarch provided a description of many reflections on spherical mirrors. He also covered the process of creating enlarged and decreased images, both real and fictitious, including the case of chirality of the images.

The concepts that the Greeks had regarding optics were revived and expanded upon by authors from the Muslim world during the Middle Ages. Al-Kindi, who lived around the year 801 and died about 873, was one of the earliest of these. He talked on the advantages of Aristotelian and Euclidean ideas of optics, but he believed that the emission theory was superior since it could better quantify optical phenomena. Ibn Sahl, a Persian mathematician, penned the treatise "On burning mirrors and lenses" in the year 984. In this work, he accurately described a law of refraction that is comparable to Snell's law. By applying this formula, he was able to determine the most effective shapes for lenses and curved mirrors. Beginning in the early 11th century, Alhazen (Ibn al-Haytham) penned the Book of Optics, also known as the Kitab al-manazir. In this work, he investigated the concepts of reflection and refraction, and he presented a new system for explaining vision and light that was based on observation and experimentation. As an alternative, he proposed the idea that light reflected in all directions in straight lines from all points of the objects being viewed and then entered the eye, despite the fact that he was unable to correctly explain how the eye captured the rays. He rejected the "emission theory" of Ptolemaic optics, which stated that the eye was responsible for emitting the rays. Around the year 1200 A.D., Alhazen's book was translated into Latin by an unknown translator, despite the fact that it was virtually forgotten in the Arabic world. It was then further summarized and elaborated upon by the Polish monk Witelo, which resulted in it becoming a classic treatise on optics in Europe for the subsequent four hundred years.

An epistemology of light, a metaphysics or cosmogony of light, an etiology or physics of light, and a theology of light, which was based on the works of Aristotle and Platonism, were some of the topics that were discussed in the writings of the English bishop Robert Grosseteste, who lived in the 13th century in medieval Europe. Grosseteste wrote on a wide range of scientific topics. Roger Bacon, the most well-known follower of Grosseteste, authored writings that cited a wide variety of recently translated works in the fields of philosophy and optics. These works included works by Alhazen, Aristotle, Avicenna, Averroes, Euclid, al-Kindi, Ptolemy, Tideus, and Constantine the African. Through the use of fragments of glass spheres as magnifying glasses, Bacon was able to demonstrate that light is reflected off objects rather than being released from them.

In the year 1286, Italy was the birthplace of the first pair of spectacles that could be worn.

The grinding and polishing of lenses for these "spectacles" was the beginning of the optical business, which began in Venice and Florence in the thirteenth century. Later on, the spectacle production centers in both the Netherlands and Germany began to produce spectacles. Rather than relying on the primitive optical theory of the time, which, for the most part, was unable to adequately explain how spectacles functioned, manufacturers of spectacles developed improved types of lenses for the purpose of correcting vision. These lenses were developed based more on empirical knowledge gained from observing the effects of the lenses. This practical development, mastery, and experimenting with lenses led directly to the invention of the compound optical microscope around the year 1595, as well as the refracting telescope in the year 1608. Both of these inventions had their beginnings in the facilities in the Netherlands that were responsible for the production of spectacles.

Johannes Kepler expanded on geometric optics in his writings at the beginning of the 17th century. He discussed lenses, reflection by flat and...