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1.DefinitionGlasses, also known as eyeglasses or spectacles['spektək(ə)lz], are usually frames bearing lenses ['lensɪz]worn in front [frʌnt] of the eyes. They are normally used for vision correction or eye protection. Sometimes glasses are worn simply for fashion purposes.2.Artifact['ɑ:təˌfækt]SunglassesPhotochromic [,fəʊtə(ʊ)'krəʊmɪk] glasses变色眼镜contact['kɒntækt] lenses隐形眼镜(美瞳)corrective glasses矫正眼镜：myopic[maɪ'ɒpɪk] glasses 近视眼镜（篮球眼镜）Presbyopic[,prezbaɪ'ɔpik] glasses 老花眼镜Astigmatic [,æstɪɡ'mætɪk] glasses散光眼镜monocle['mɒnək(ə)l] 单片眼镜3D glassesadjustable myopia[maɪ'əʊpɪə] glassesother functional glasses3.How It WorksSunglassesSunglasses allow better vision in bright daylight, and may protect one's eyes against damage from high levels of ultraviolet [ʌltrə'vaɪələt]light, which is due to metal powder['paʊdə] filters ['fɪltə]——a kind of equipment that can select the incident light. Tinted ['tintid] glasses can selectively absorb parts of the sun light’s band, because of the very thin metal['met(ə)l] powder (iron['aɪən], copper['kɒpə], nickel['nɪk(ə)l] , etc[ɪt'setərə, et-].). In fact, when the light on the lenses, based on the so-called "destructive[dɪ'strʌktɪv] interference[ɪntə'fɪər(ə)ns]" process, the light is reduced.Destructive interference depends on the refractive[rɪ'fræktɪv]index['ɪndeks]of lenses (i.e., the degree of deviation[diːvɪ'eɪʃ(ə)n]occurred when the light pass through different materials in the air ).photochromic [,fəʊtə(ʊ)'krəʊmɪk]glassesA kind of special glasses is called the photochromic[,fəʊtə(ʊ)'krəʊmɪk]glasses. In the process of manufacturing, the light sensitive['sensɪtɪv] materials, such as silver ['sɪlvə] chloride['klɔːraɪd] , silver bromide['brəʊmaɪd] (generally called silver halide['heɪlaɪd] ) and a small amount of copper oxide catalyst['kæt(ə)lɪst]are mixed into in advance. Silver halide makes lens from colorless to light gray, tan, from black glasses back to ordinary glasses, just like a magic. Silver halide is easy to see light decomposition[,diːkɒmpə'zɪʃn] and then turns into lots of black silver particles evenly distributed in the glass, so glass lenses look dim, this is the black glasses. When the place becomes slightly dark, silver and halogen['hælədʒ(ə)n; 'heɪl-] compound['kɒmpaʊnd]and generate['dʒenəreɪt]silver halide under the promoting of copper oxide catalyst,therefore, glass lenses became more transparent.corrective glassesmyopic glassesConcave['kɒnkeɪv] lens is mainly used to correct myopia. Concave lens has the effecton divergent light, and it can form a contractible[kən'træktibəl]and upright virtual ['vɜːtjʊəl] image['ɪmɪdʒ], so that the image distance become longer and just fall in the retina ['retɪnə] .Presbyopic glassesPresbyopic[,prezbi'ɔpik]lens is Convex ['kɒnveks]lens. Parallel['pærəlel]light (such assunlight)which parallels to the main optical axis['æksɪs] (the attachment of convex lenstwo spherical ['sferɪk(ə)l] globes called the main axis of the lens) into convex lens, andfocus on a point on the axis after the light refracts [rɪ'frækt] on both sides of the lens.(mark for F)3D glassesSpecialized glasses may be used for viewing specific visual ['vɪʒjʊəl]information (such as stereoscopy[,sterɪ'ɒskəpɪ] ——3D).The illusion[ɪ'l(j)uːʒ(ə)n] of three dimensions [dɪ'menʃənz] on a two dimensional surface can be created by providing each eye with different visual information. 3D glasses create the illusion of three dimensions by filtering['fɪltərɪŋ] a signal ['sɪgn(ə)l] containing information for both eyes. The signal, often light reflected off a movie screen or emitted from an electronic[ɪlek'trɒnɪk] display, is filtered so that each eye receives a slightly different image.ter developmentsDespite the increasing popularity of laser corrective eye surgery['sɜːdʒ(ə)rɪ], glasses remain very common, as their technology has improved. For instance, it is now possible to purchase frames made of special memory metal alloys['ælɔiz] that return to their correct shape after being bent. These designs offers dramatically[drə'mætɪkəlɪ]better ability to withstand the stresses of daily wear and the occasional accident. Modern frames are also often made from strong, light-weight materials such as titanium[taɪ'teɪnɪəm] alloys['ælɔiz], which were not available in earlier times. /wiki/Glasses。