Democritus from Abdera, who lived in the 5th century BC, expressed the opinion that everything in this world is conditional, only atoms and void are reality. Historical documents have been preserved, confirming his authorship of the concept of light as a stream of particles, which are endowed with certain physical properties. But the concept of “optics” will appear later. The seeds of Democritus from Abdera, sown in the process of comprehending the structure of light, have sprouted.
The history of the origin of the word optics
In the third century BC, the ancient Greek scholar Euclid formulated the laws of the propagation of light in the treatise "Optics". In fact, this event can be considered the origin of geometric (or linear) optics. After the appearance of an attempt to systematize knowledge about the properties of light, many centuries passed before a set of theories and laws took shape in science.
The unsolved question for a long time remained the nature of the origin of color. Opinions were expressed that color is a mixture of light and darkness in different proportions (Aristotle), as well as a version about different speeds of rotation of light particles (Descartes).
A real breakthrough was the discovery of the 17th century in the field of wave optics. But the construction version of what optics explained the existence of diffraction, interference and other properties of light did not exist. The dominance of the corpuscular theory of the origin of light shook Newton. He was well aware of the pros and cons of both corpuscular and wave theories.
Therefore, in his treatise "Optics" the mathematical model of the particle-wave theory of light is spelled out in detail. The basic concepts of optics (wave or physical) are built on Newtonian models. The description of the propagation of light waves contains the Huygens-Fresnel principle, which became the basis for the development of physical theory.
Only at the beginning of the 19th century, Classical optics acquired its features, recognizable by contemporaries, and appeared as a science.
The meaning of the term
The term of Greek origin (ὀπτική - the doctrine of visual perceptions) in modern life has several interpretations: a section of such a science as physics and, often used in everyday life, collective meaning.
What is optics as a field of physics? This is a section in which the features of the propagation of light in different environmental conditions and the interaction with various substances are studied. The definition of optics in physics is based on the phenomena studied, therefore, there is a division into classical and quantum optics. At the same time, the first view is represented by geometric (ray) and physical (wave) sections.
The meaning of the word optics in everyday life is of a collective nature and is used to designate instruments, tools that use the laws of the above science.
Optics as a branch of science
A field of physics that studies the propagation of wide-range electromagnetic waves (visible, infrared, ultraviolet, x-rays and gamma rays). Their properties and characteristics are given in the table below.
Types of radiation | Frequency Hz | Length / m | The properties | A source |
Infrared radiation | from 10 12 up to 3.75 × 10 14 | 30 × 10 -4 8 × 10 -7 | Reflection, diffraction, refraction, polarization | Thermal photocopying, electric fireplace. |
Visible light | 7.5 × 10 14 | 4 × 10 -7 | Reflection, diffraction, refraction, polarization | Incandescent lightning. |
Ultraviolet radiation | 3 × 10 17 | 10 -9 | photochemical | Carbon arc |
X-ray radiation | 3 × 10 20 | 10 -12 | Penetration, diffraction | X-ray tube |
Gamma radiation | 10 23 | 3 × 10 -15 | Space processes, nuclear processes | Cyclotron, Cobalt 60 |
A variety of sections of optics corresponds to the number of investigated processes:
Classic optics | Quantum optics |
Geometric (or linear) A light beam (propagating in a homogeneous medium) is considered as a line that changes direction according to certain rules during reflection and refraction. Light as a wave is not considered. | Physical (or wave) The interaction of light and electromagnetic rays with dissimilar media (substances). | Quantum optics studies the manifestations of the quantum characteristics of light, as well as the interaction with substances based on the quantum structure of objects and special propagation conditions. |
Adaptive optics - studies the possibilities of correcting irregular distortions in the distribution of light in an inhomogeneous medium based on optical controlled elements. | Crystal optics - studies the propagation of light in anisotropic media and crystals through consideration of the phenomena of birefringence, polarization of light, etc. | Laser physics - studies the principles of the operation of lasers and the possibilities of their application in research, medicine, industry and other areas of society. |
Integrated Optics - studies wave propagation in planar optical waveguides. |
Gradient optics - studies the optical properties of substances with varying refractive indices by coordinates (puddles on asphalt on a hot day). | X-ray optics is an applied industry that tracks the propagation of X-ray rays in different environments. | Nonlinear optics - studies light phenomena when interacting with substances that have a nonlinear polarization reaction to the electric field of a wave. |
Electronic optics - explores the features of focusing, transportation in magnetic and electric fields of charged particles. | | |
The classification of the optics section corresponds to the historical development of the doctrine of the properties of light:
- geometric - 3rd century BC (Euclid);
- physical - 17th century (Huygens);
- quantum - 20th century (Plank).
Geometric or Euclidean optics
In the 3rd century BC, scientists were more interested in the laws of the propagation of light than in its nature. Hence the definition of optics as the science of the propagation of a light beam in a homogeneous medium.
By studying the motion of a ray of light, many phenomena were clarified: the formation of rainbows, mirages, and the curvature of rays. Methods of geometric optics are used by contemporaries in the design of various optical devices.
Features of beam optics consist in taking into account and studying rays incident at small angles to the axis, which simplifies theoretical calculations. This effect, called the paraxial approximation, is used in many optical instruments.
Physical optics
The doctrine of the wave nature of phenomena arose from numerous observations and experiments that do not fall under the description of the theory of beam propagation. What is wave optics? It is often called the Huygen, however, the Dutch physicist rather summed up the research of his contemporaries than discovered new laws. This fact does not detract from his contribution to the development of the industry.
The basis for the emergence of the Huygens-Fresnel principle, known today, was the work of no less famous scientists Robert Hook and Isaac Newton. The treatise “Optics” of the latter can be regarded as an attempt to unite the corpuscular and wave theories that existed at that time.
It should be noted that physical optics, studying the distribution of complex pulses by means of optical systems taking into account the amplitude and phase of the wave, appeared only at the beginning of the 19th century. Currently, in this section of optics, a systematization of calculations is being carried out to more fully describe the models under consideration.
Quantum optics
What is photon optics? The idea of describing an electromagnetic field using quanta at the beginning of the 20th century was put forward by Max Planck. He suggested that the radiation of light occurs in certain parts - quanta. It was further proved that it is not only partially emitted, but also absorbed. This allowed Albert Einstein to draw a conclusion about the discrete structure of light.
After some time, light quanta began to be called photons, and the flux was considered as a group of particles. Thus, in quantum optics, light was considered both as a wave and as a stream of particles at the same time, since phenomena such as diffraction and interference cannot be explained by the flow of photons.
In the mid-20th century, the Brown-Twiss experiment made it possible to clarify the area of application of quantum optics. They proved that a certain number of light sources emitting photons to two photodetectors, which give an audio signal about the registration of particles, can cause the devices to work simultaneously. The experiment was conducted with different light sources.
After that, conclusions were drawn about the existence of light with pair correlation of photons (for sources with simultaneous operation of the signal at the receivers) and with the anti-grouping of light particles (for sources that never allow the simultaneous operation of receivers).
Experience has proved the division of light into two- and single-photon. From this we can conclude that there are states of light that cannot be explained using classical optics, they are called non-classical. The development of the practical application of non-classical light leads to amazing results. Therefore, quantum optics is a modern direction with extensive capabilities in the study and application.
Physiological optics
This section is considered interdisciplinary for a number of reasons. Given the laws of optics, it is based on such sciences as biophysics, biochemistry, psychology of visual perception, developmental psychology and physiology. It has a practical direction. All elements of the visual apparatus are studied. Attention is paid to rare phenomena, for example, optical illusion.
The research results are used in medicine, physiology, optical technology, the film industry.
Optics. What can i buy?
At the household level, the word optics is more often used as the name of the store. Naturally, in it you can buy a variety of technical optics devices - glasses, lenses, corrective and protecting eyesight mechanisms. At the present stage, the equipment of such institutions allows on-site determination of visual acuity, existing problems and methods for their elimination. Choose lenses with the desired effect and place an order, or purchase ready-made goods.
Finally
After many centuries, one can be sure that Democritus from Abdera was still right about the particles and the void, and that every person decides whether or not everything else exists.