The mysterious light and its effects of occurrence good morning science electricity dance moms song

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Light plays as a backbone for all the daily activities we perform in life. From time immemorial, eminent philosophers and scientists of different genres had tried to unveil the mystery behind it and were able to enrich our knowledge and designate the branch of science as Optics. The amazing view of the Aurora Borealis formed in Iceland.

Form the work of various philosopher-scientists of ancient time it is observed that, simple phenomena of light like Reflection and Refraction can be explained easily if the path of the light is considered to be a straight line. In 1675, Sir Isaac Newton put forward the historical theory about the nature of light. Newton in his ‘ Corpuscular Theory of Light’ stated that light consisted of corpuscles which were a stream of discrete, tiny and perfectly elastic particles. According to this theory, different colors of light are due to different sizes and masses of the particles. Reflection and Refraction are well explained with the help of this theory. However, it fails to explain some other phenomena of light such as Interference, Diffraction, and Polarization. At the same time in 1960, Christiaan Huygens put forward another theory of light – ‘Wave Theory of Light .’ In this theory, Huygens considered light as a longitudinal wave just like a sound wave. With the Wave theory, the phenomena of Reflection, Refraction, and Interference of light can be explained, but it fails to explain Diffraction and Polarization of light. After 100 years Augustin Jean Fresnel slightly modified the Huygens’ wave theory and included the additional concept of Interference and was able to explain Diffraction and Polarization. To do so, Fresnel had considered the light wave as a transverse wave instead of a longitudinal wave. This new concept of light proposed by Huygens and developed by Fresnel was completed by Maxwell with his Electromagnetic Theory. Maxwell proved that light is a kind of wave named Electromagnetic wave. By his famous equations (a set of four partial differential equations) he was able to define light similar to electricity and magnetism. On solving two of those equations, one can recognize the wave that moves with the velocity of light. This wave is known as the Electromagnetic wave. From his study, Maxwell observed that the wave showed the same nature to that of light and was confirmed that light was also an Electromagnetic wave. He guessed the existence of different electromagnetic waves having different frequencies that propagated with velocities equal to the speed of light. The lights of different colors we observe by our naked eye are actually the electromagnetic waves of different frequencies.

Till the end of the nineteenth-century wave theory of light was considered as a completely successful theory since every phenomenon of light were well explained with the aid of this theory. In 1887 Hertz discovered the ‘Photoelectric Effect.’ Scientists faced difficulties when they had failed to explain this effect with wave theory and the drawbacks of the theory had become the new topic of discussions. The Photoelectric Effect is nothing but the emission of electrons due to the incident of the light on a metal surface. In 1995 Albert Einstein put forward ‘Quantum Theory of Light’ based on Max Planck’s quantum theory and was able to explicate Photoelectric Effect. Einstein considered light as a bundle of small particles- photon. He assumed (on the basis of Planck’s formula) that if the frequency of the light of a particular color is f, then the energy of the photon of that color would be hf and formulated an equation for the kinetic energy of the emitted electron during Photoelectric Effect. Nevertheless, the scientists get confused about the nature of light, whether it was particle or wave. Because almost all phenomena of light such as Reflection, Refraction, Interference, Diffraction, and Polarization were well explained with the wave nature of light but on assuming light as particles those phenomena were not explainable. At last, French physicist Louis de Broglie had ended that perplexity by his hypothesis. De Broglie coupled the energy equations of Planck’s quantum theory, i.e., E = hf and Einstein’s Theory of Relativity, i.e., E = mc 2and proposed a new hypothesis. De Broglie proposed that light shows both particle and wave nature simultaneously. Finally, the quantum theory accepted the dual nature (wave and particle) of light and was able to clarify every phenomenon of light. An illustration to show the photoelectric effect. (Source: Wikipedia)

Besides the Photoelectric Effect, Einstein experimented on absorption and radiation of light and other electromagnetic waves by matter and demonstrated two kinds of radiation: Spontaneous Emission and Stimulated Emission. The atom or molecule in the excited state can de-excite spontaneously to the ground state by radiating energy. This process of emission is known as Spontaneous Emission. On another hand, if the atom or the molecule in the excited state de-excites to its ground state by the influence of a photon having energy equal to the difference between the energies of the two levels, then the process of emission is known as Stimulated Emission. In the case of Stimulated Emission, the energy, phase, polarization state and, the direction of motion of the emitted photon is similar to those of excited/incident photon. Thus, with the help of stimulated emission, the light passing through a collection of atoms or molecules can be amplified. After that, scientists had developed a new tool named LASER (Light Amplification by Stimulated Emission of Radiation) which is very familiar to all of us. The invention of LASER manifested a new world of the practical applications of light. The fastest communication system of present days, the Optical Fibre Communication System was developed with the aid of Optical Fibre which is fabricated using LASER and the idea of total internal reflection. Signals (data) can be transmitted with the speed of light from one place to another without any disturbance only because of Optical Fibre Communication System.

The story about the contribution of light on the development of human culture and advancement of Science and Technology has no end. It is come to know that lens was used since the ancient days. We all are familiar with the contributions of microscope and telescope to the Science and Technology. Moreover, light occupies an important place in Art and Literature also. In writers word, light is the symbol of boundless aspiration, natural grace and a good time. After the success of the ‘International Year of Light’ in 2015, this year the UNESCO has declared the 16th of May as the ‘International Day of Light’ to cherish the contributions of light in different fields such as science, culture, art, education, sustainable development, medical, communication, and energy etc. Today, on the very special occasion of the first ‘International Day of Light’ the Good Morning Science team wish you a bright life enlightened with the sparks of prosperity.