Light - Explanation and definition of light

What is light

Light is defined as electromagnetic wave that is composed of tiny particles called photons and allowing us to view everything around us bringing color and sense of sight.

Although this definition may seem difficult to understand will explain each step of the information mentioned above in the definition of light.

When we throw a stone into a pond we note that a series of waves move through the water surface, like wave of the pond light is an electromagnetic wave, it is a wave with an electric part and another magnetic part, unlike pond wave that need water to propagate the electromagnetic waves do not require any medium, electromagnetic waves propagate through the empty space.

Any wave has 4 properties or characteristics as it canidentify, these are the amplitude, frequency, speed and wavelength. The wavelength is the distance between two crests or troughs of the wave, visible light which is perceived by the human eye and allows us to see everything that surrounds us is the part of the electromagnetic wave that has a wavelength between 380 and 740 nanometres, so the light as we understand it is a small portion of length of electromagnetic waves that emits light sources like the sun, the stars or lamps in your home.

Finally photons are the fundamental and indivisible particles without mass or charge that compound light, photons are like little balls that vibrate and behave like a wave when moving and as particle when interacts with a body, thus being corpuscle and wave simultaneously.

The colors that we perceive are merely sensations to the human eye that interprets different vibrations of photons, for example the red color corresponds to 4 x 1014 vibrations per second and the blue color corresponds to 6.5 x 1014 vibrations per second,when there are a number of photons which vibrate at different frequencies we obtain a mixture of all colors which gives as result white light.

Electromagnetic spectrum represents wavelength, frequency and energy that you can find an electromagnetic wave, the spectrum is divided into different bands where waves share certain characteristics, for example the band of gamma rays, ultraviolet, visible light, infrared or microwave. In the band of visible light are shown as a function of frequency (vibrations per second) or a different wavelength range of colors made visible light. You can observe it in the picture below.

This set of tiny particles called photons that make up light, theoretically acquire the maximum speed that any particle of the universe can be achieved in a vacuum, with approximately 3 10 8 m/s, in 1 second a photon would nearly 4, 5 laps around our Earth planet.

This speed is considered a universal constant and is used among other things to indicate astronomical distances between stars, galaxies or clusters, for example the planet Venus is at a distance of 0.000011 light years away, the nearest star of our planet is approximately 4,3 light years and the most distant galaxy known currently is about 13,200 million light years, no doubt the universe is extraordinarily large. 1 light year is the distance travelledby a photon in a year or 5,88 trillions milles.

Discovery of light

The ancient Greek philosophers were the first to consider the nature and source of light, we see questions like whycan we see? Or why an image changes when we see it through the water? Attempted to be answered by a logical and convincing approach. In 500 BC the Greek philosopher Empedocles released the first theory about the nature of light, colloquially known as the theory of the lighthouse, is identified as the light rays emanating from our eyes impacting with objects allowing us to see everything around us.

1500 years must past until the Arab mathematician Alhazen discovered that the eyes were not emitting light the eyes has receptors of the light, Alhazen which had a remarkable mathematical basis, was the first physicist to investigate the properties of light such as reflection and refraction discovering that light was governed under universal laws and itcould be represented by mathematics.

In the seventeenth century a scientific battle between different physicists, mathematicians and intellectuals of the time were engaged, on the one hand the great physicist and mathematician Sir Isaac Newton demonstrated that white light is made up of a wide range of colors which he called spectrum , for it passed a beam of light through a prism, also Newton argued that light was formed of small particles or corpuscles, the corpuscular theory was rejected by other physicists and mathematicians of the stature of Hooke or Hugens, which defended the nature of light as a wave and not as a particle.

During the following centuries the wave theory of light was moving to the corpuscular theory of Newton, intrinsic properties of light such as interference, reflection, diffraction and polarization were accurately represented and explained through the use of the waves. But in the late nineteenth century German physicist Hertz discovered the photoelectric effect of light, this being impossible to explain by using waves, particles or corpuscles was needed to explain it.

The great physicist and mathematician Albert Einstein demonstrated that the photoelectric effect could be explained by the use of small corpuscles (quanta of energy) that he called photons, subsequently experiments of double slit made by Thomas Young confirmed the wave-particle duality of the light, quantum physics was born and she had reconciled 2 theories confirming that light behaved both as a particle and as a wave.

Importance of light

Undoubtedly the light exerts a huge influence on all living creatures on our planet, plant and animal life depends directly on its presence, chemical processes such as photosynthesis, the creation of vitamin D or simply biological clock that marks the activity and rest processes are closely linked with the presence of light.

Thousands of species of plants and organisms such as trees, algae and bacteria directly depend on sunlight for the process of photosynthesis, converting light into chemical energy that nourishes and allows them to grow and develop, photosynthesis is the most important biochemical process of our planet as it is the source of generation of oxygen to the atmosphere and keeps the nutritional balance by allowing grow plants and vegetables that will later be food for other species.

Light exerts a huge influence in our lives;if we do not have light we do not have the sense of sight and could not see anything around us. Vitamin D necessary for our body is produced by the action of ultraviolet light from the sun, transforming part of our cholesterol in this valuable vitamin.

The duration of day and night is delimited by the presence or absence of light, plants and all living things on our planet are regulated by this biological clock that tells us when we started our daily activity and when we need rest, on the other hand since ancient light has indirectly defined the length of the days, months and seasons.

Even in religions around the world has greatly influenced, the ancient Egyptians worshiped the God Ra symbol of sunlight and source of life, millions of religious worldwide refer to God as the creative light, light divine or the true light.

On the other hand thousands of studies link the absence of light as a cause of discouragement, apathy, stress and even depression, the ancient physicians Greek kneed the healing properties of sunlight and were the forerunners of sunbathing as medicine to cure various diseases of their patients. Who does not like a peaceful, relaxing and fun day at the beach?

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