{"id":237,"date":"2023-04-16T05:09:27","date_gmt":"2023-04-16T05:09:27","guid":{"rendered":"https:\/\/web.htk.tlu.ee\/stem\/stem2\/?post_type=chapter&p=237"},"modified":"2023-04-16T05:52:59","modified_gmt":"2023-04-16T05:52:59","slug":"unit-1-introduction-into-interferometry","status":"publish","type":"chapter","link":"https:\/\/web.htk.tlu.ee\/stem\/stem2\/chapter\/unit-1-introduction-into-interferometry\/","title":{"rendered":"Unit 1: Introduction into Interferometry"},"content":{"raw":"

1.1 A short History of Light<\/h1>\r\n\r\n\r\n\r\n\r\n\r\n\r\n
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Isaac Newton<\/strong>\u00a0<\/span>(1643-1727) states that light is composed of tiny particles (corpuscles) of different color properties that are ejected from a light source and propagate in a straight line as long as they do not encounter any obstacles.<\/span><\/p>\r\n\r\n

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  • This theory explains why bodies cast sharp shadows.<\/li>\r\n \t
  • Refraction is being interpreted as the result of an attraction that the refractive medium exerts on the light particles. However, the prediction that followed from this idea, that the more refractive the medium, the greater the speed of light, was later experimentally disproved.<\/li>\r\n<\/ul>\r\n<\/td>\r\n
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Christiaan Huygens<\/strong>\u00a0(1629-1695) compared the processes of propagation, reflection and refraction of light with those of waves on a water surface.<\/p>\r\n\r\n

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  • Explanation of the Law of Reflection by the principle of elementary waves (Huygens\u2019 principle)<\/li>\r\n \t
  • Explanation of refraction with the same principle, assuming different velocities of light in different mediums<\/li>\r\n<\/ul>\r\n<\/td>\r\n
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James Clerk Maxwell<\/strong>\u00a0(1831-1879) stated that light is an electromagnetic wave.<\/p>\r\n\r\n

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  • Quantitative explanation of the relationship between electric and magnetic fields<\/li>\r\n \t
  • Reduction of the speed of light to other elementary natural constants: c = (\u03b50\u00b7\u03bc0)\u00bd<\/li>\r\n<\/ul>\r\n<\/td>\r\n
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Albert Einstein<\/strong>\u00a0(1831-1879) found out that the energy of a light is contained in localized portions of size h\u00b7f, the light quanta or photons.<\/span><\/p>\r\n\r\n

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  • Explanation of the photoelectric effect<\/li>\r\n \t
  • Explanation of the Compton-effect<\/li>\r\n \t
  • On the other hand, the light quantum concept is not suitable for describing diffraction and interference phenomena.<\/li>\r\n<\/ul>\r\n<\/td>\r\n
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Task 1.1<\/h2>\r\nName the characteristic quantities of a wave.\r\n\r\n[h5p id=\"22\"]\r\n\r\n
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Task 1.2<\/strong><\/h2>\r\nDesign your own wave by using the following worksheet!\r\n\r\n\"\"<\/a>\r\n\r\n
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1.2 Light + Light = Darkness?<\/h1>\r\n[caption id=\"attachment_242\" align=\"aligncenter\" width=\"436\"]\"\" Figure 3:<\/strong> The emitted light of two incandescent lamps does not constructively overlap.<\/em>[\/caption]\r\n\r\nSuperposition of the light of two lightbulbs:\r\n