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OPTICS Optics • Study of light and its properties Light • Light helps us to see • Light may be defined as an electromagnetic energy Uses of Light • Sun light helps in the preparation of Vitamin D in our body • Light helps in photosynthesis in plants Travel in light • Light travel in a straight line • Light travel as a wave • Particle nature of light Properties of light • Light gets reflection from the smooth surface and reflection gives images • Light gets refracted when light goes from one medium to another medium the part of light in bend Types of Optics • Physical optics • Physiological optics • Geometrical optics Physical optics • Wave optics • Quantum optics Wave optics In it light is treated as a Wave * Interference (i) Constructive (ii) Destructive * Diffraction (i) Fresnel (ii)Fraunhofer * Polarization Wave optics Interference • When Two waves of light travel along the same path the effect produced depends upon whether or not the ways are in phase with one another. Constructive • If they are in phase the resultant wave will be a summation of the two and this is called Constructive interference Destructive • If the Two waves of equal amplitude are out of phase by half a cycle, they will cancel each other Destructive interference. Diffraction Diffraction • When a wave front encounters a narrow opening or the edge of an obstruction the wave motion spread out on the far side of obstruction. It is as if the edge of the obstruction acts as a new center from which secondary wave fronts are produced which are out of phase with the secondary wave this phenomenon is called diffraction. Polarization • Light waves are traveling may or may not be parallel to each other. If direction are randomly related to each other the light is unpolarized / non polarized. If parallel to each other is called polarized light. Quantum optics • Scattering of light • Transmission and absorption • Laser Geometrical optics LAWS OF REFLECTION • The incident ray, reflected ray and the normal ray to the reflecting surface all lie in the same plane. • Angle of incidence(i) = Angle of reflection(r) incident ray normal reflected ray i r LAWS OF REFRACTION Incident ray, refracted ray normal at the point of incidence are all in the same plane. The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant for a given pair of media for a given colour. The constant is known as refractive index of the second medium with respect to first medium. REFRACTION OF LIGHT • Refraction is defined as the change in direction of light when it passes from one transparent medium into another of different optical density. Rarer medium Denser medium Denser medium Rarer medium REFRACTION THROUGH A TRIANGULAR GLASS PRISM REFRACTIVE INDEX • A comparison of the velocity of light in a vacuum and in another medium gives a measure of the optical density of that medium. This measurement is called the absolute refractive index,(n) of the medium. Absolute refractive index = velocity of light in vacuum velocity of light in medium • Refractive index of ; Air-1 Water-1.33 Cornea-1.37 Crystalline lens-1.38-1.42 Crown glass- 1.52 Flint glass- 1.6 Diamond- 2.5 CRITICAL ANGLE AND TOTAL INTERNAL REFLECTION • When the angle of refraction in the rarer medium is 90 degree, the angle of incidence in the denser medium is known as the critical angle of the denser medium. • When the angle of incidence in the denser medium is more than the critical angle,that ray cannot be refracted obeying the law of reflection • Diagram Thank you