• What is light
• History of light
• Characteristics of the light
• Propagation of light
• Phenomena of light
• Sunlight and artificial light

We explain everything about light, the history of its study, how it spreads and other characteristics. In addition, natural and artificial light.

Light is a form of electromagnetic radiation visible to the human eye.

What is light

What we call light is the part of electromagnetic spectrum that can be perceived by the human eye. There are, apart from light, various forms of electromagnetic radiation in the universe, which spreads through the space and transports Energy from one place to another (such as ultraviolet radiation or x-rays), but none of them can be perceived naturally.

Visible light is made up of photons (from the Greek word phos, "light"), a kind of particles elementals lacking mass. Photons behave in a dual way: as waves and as particles. This duality endows light with unique physical properties.

The optics is the branch of the physical that studies light, its properties, behavior, interaction and its effects on the matter. However, light is the study of many other disciplines as the chemistry, general relativity or physics quantum, among other.

History of light

The nature of light has intrigued the human race forever. In ancient times it was considered a property of matter, something that emanated from things. It was also linked to the Sun, the star king in most of the religions Y worldviews of the humanity primitive and therefore also with the heat and with the life.

The ancient Greeks understood light as something close to the truth of things. It was studied by philosophers like Empedocles and Euclides, who had already discovered several of its physical properties. From Renaissance In Europe, in the fifteenth century its study and application to human life took a great boost, with the development of modern physics and optics.

Subsequently, the management of the electricity allowed artificial lighting of homes and cities, ceasing to depend on the Sun or burning fuels (diesel or kerosene lamps). Thus the foundations of optical engineering that developed in the twentieth century were sown.

Thanks to electronics and optics it was possible to develop applications for light that centuries ago would have been unthinkable. Our understanding of its physical workings increased, in part thanks to quantum theories and the enormous advancement in physics and chemistry that took place thanks to them.

Thanks to the light and its study exist technologies as disparate as lasers, movie theater, the Photography, photocopying or photovoltaic panels.

Characteristics of the light

All colors are contained in light.

Light is an undulatory and corpuscular emission of photons, that is, at the same time it behaves as if it were made of waves and matter.

It always travels in a straight line, at a defined and constant speed. The frequency of light waves determines the level of light energy, and it is what differentiates visible light from other forms of radiation.

Although light in general (both from the Sun and from a lamp) looks white, it contains waves with wavelengths that correspond to each color in the visible spectrum.

This can be evidenced by pointing it at a prism and breaking it down into the tones of the Rainbow. That an object has a particular color is a consequence of the object's pigment absorbing certain wavelengths and reflecting others, reflecting the wavelength of the object. color What we see.

If we see an object white, it is because the pigment reflects all the light that is emitted on it, all the wavelengths. If, on the other hand, we see it black, it is because it absorbs all the light and nothing is reflected, we see nothing, that is, we see black.The colors of the spectrum perceptible by our eye range from red (700 nanometers of wavelength) to violet (400 nanometers of wavelength).

Propagation of light

Light travels in a straight line and at a speed of 299,792,4458 meters per second in a vacuum. If it has to go through dense or complex media, it moves at slower speeds.

Danish astronomer Ole Roemer made the first rough measurement of the speed of light in 1676. Since then, physics has greatly fine-tuned the mechanisms of measurement.

The phenomenon of shadows also has to do with the propagation of light: when hitting an opaque object, the light projects its silhouette on the background, outlining the portion blocked by the object. There are two degrees of shade: a brighter one, called penumbra; and another darker, called umbra.

Geometry has been an important tool when studying the propagation of light or designing artifacts to obtain certain effects, for example, the telescope and the microscope.

Phenomena of light

Refraction in this figure occurs because the speed of light decreases as it passes through water.

The phenomena of light are alterations that it experiences when subjected to certain media or certain physical conditions. Many of them are visible on a daily basis, even if we don't really know how they operate.

• Reflection. When hitting certain surfaces, the light is capable of "bouncing", that is, of changing its trajectory at certain and predictable angles. For example, if the object hitting at a certain angle is smooth and has reflective properties (such as the surface of a mirror), the light will be reflected at an angle equal to the incident, but in the opposite direction. This is how mirrors work.
• Refraction. When light passes from one transparent medium to another, with different densities there is a phenomenon known as "refraction." The classic example is the passage of light between the air (less dense) and the Water (denser), which can be evidenced by placing a cutlery in a glass of water and noticing how the image of the cutlery seems to be interrupted and duplicated, as if there were an "error" in the image. This is because water changes the direction of propagation when passing from one medium to the other.
• Diffraction. When light rays surround an object or pass through openings in an opaque body, they will experience a change in their trajectory, producing an opening effect, as occurs with car headlights at night. This phenomenon is typical of all waves.
• The dispersion. This property of light is what allows us to obtain the full color spectrum by scattering the beam of light, that is, it is what happens when we make it go through a prism, or what happens when light passes through the raindrops in the atmosphere and thus generates a rainbow.
• Polarization. Light is made up of oscillations of the electric field Y magnetic which can have different addresses. The polarization of light is a phenomenon that occurs when, for example, by means of a polarizer (such as sunglasses) the oscillation directions are decreased so that the light spreads with less intensity.

Sunlight and artificial light

The traditional light source of humanity has been that coming from the Sun, which constantly radiates visible light, heat, ultraviolet light and other types of radiation.

The sunlight It is essential for the photosynthesis and to maintain the temperature of the planet within ranges compatible with life. It is similar to the light that we observe from the other stars of the galaxy, even though they are billions of miles apart.

From very early times the human being has tried to imitate that source of natural light. Initially it did so by mastering fire, with torches and bonfires that required combustible materials and were not very durable.

Later he used wax candles that burned in a controlled way, and much later he created streetlights that burned oil or other hydrocarbons, giving rise to the first urban lighting network, which was later replaced by natural gas. Eventually it came to the use of electricity, its safer and more efficient version.