How is Light formed?

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What is light? Simply put it is something that takes away darkness. We see so much of it around us that we don't know exactly how to describe it. In many places round the world light has been associated with auspiciousness. It is celebrated. But then what exactly is light. It is the visible part of the electromagnetic spectrum which our eyes can see and perceive. There are other types of light as well which the normal eye cannot see such as the UV light and infrared light.


How is light formed?

There have been many theories trying to understand the nature of light scientifically. The reason being light behaves as both particles and waves. It was theorized in the beginning that it was a particle but then evolved to explain that it was a wave. This dual feature of light is known as wave-particle duality. To understand the concept of light in the form of wave first because light is nothing but a wave coming from the electromagnetic spectrum and which varies from radio wave to gamma wave. To  understand this process better, when you throw a stone in a body of water, a wave is created. But the water remains at the same place and does not move. The wave is created because you have put your mechanical energy into it which is moving like a wave. Similarly, all the waves existing in nature travel due to some form of energy. Electromagnetic radiation are formed from the fluctuations or variations in electrical and magnetic fields. These waves make it possible for the energy to be transported from one place to another. The light visible to us is emitted by photons which behave as both wave and particles.


What is  an  Electromagnetic Spectrum?

Electromagnetic spectrum is made up of electromagnetic waves which are arranged in different wavelength and frequencies. The longest waves on electromagnetic spectrum are the radio waves. These are ones used as signals for radio and range from 1000 meters to 1 cm. Microwaves are used for heating in domestic appliances and also in radar and range from 1 tenth of mm to 1cm. Infra red radiation are used for heating and their wavelength range from sub-millimeters to micrometers.  The light which we see has the wavelength ranging from 380- 790 nm and at travels at a speed of 186,300 miles per second.  Other light includes ultra violet rays, X rays and gamma rays.


How do light waves travel?

Light does not necessarily need any medium to travel. Light can travel in a vacuum as well. The photons in the light wave vibrate at right angles in the direction of movement of electrical and magnetic field and also at right angle to each other. These light waves are of varying sizes and the distance between the two waves is termed as wavelength which is measured from peak to peak from two points of successive waves.


How do we detect light?

Study of light guides us to the knowledge of various light related phenomenon in the galaxies of this universe and even better understand the reaction of living cells with light (photosynthesis is a natural process which also makes use of light to prepare food in plants and in some microbes as well).These phenomenon or reactions take place when light interacts with the ions or atoms of the matter particles. The atoms or molecules of matter which are at ground level energy  absorb energy and  reach a higher state. When they release energy and comeback down to a lower energy state, light is emitted in the visible spectrum. This is how light becomes visible to us.


What are some special characteristics of photon?

As a photon or particle light displays some special characteristics which have come to fore just recently. Some of them are given below:

  • All single photons have permanent, energy level which is specified and discreet.
  • Each light color has its own distinct energy level. This energy cannot be increased or decreased without changing the wavelength of light.
  • So as to change the intensity of light the number of photons is needed to be decreased or increased.


What are the properties of light?

Refraction and reflection are the two properties of light. Reflection is the first property of light. In case of reflection the angle of incidence and the angle of reflection are equal. When a light passes and bends through different intensity of material, the process is called refraction.

n =c/v ( where v is speed of light for that particular material)


What are the different ways in which light is emitted?

There are different ways in which light is emitted. Some of the various excitation sources of light are

  • Chemiluminescence : This is luminescence produced due to energy released  during a chemical reaction of a substance

  • Cathodeluminescence  : is the light or luminescence produced when an electron(cathode beam) beam hits a substance, examples are Television, oscilloscope, computers.
  • Sonoluminescence : This is emission of light by tiny bubbles suspended in a liquid which are exposed to intense acoustic fields. This field has not been studied as much.
  • Triboluminescence : This is luminescence produced due to scratching, ripping or twisting  of a substance. This is light caused by friction. The safety light sticks used for Halloween are of this type.
  • How does Bio-luminescence work? : Is the production of light by a living organism, the firefly is a well known example.
  • Thermoluminescence : Is the luminescence produced by some crystalline minerals where previously absorbed energy is re-emitted as light on heating the mineral. This is used in dating buried objects
  • Electroluminescence : Is the light produced due to the flow of electrons in certain crystals.
  • Photoluminescence: Is the luminescence produced by a substance  due to absorption of electromagnetic radiation, mostly used in Fire exit signs.
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