The most important invention-Light,Introduction,The First Electric Light Made in 1809 by Hunphry Davy,this is called the electric arc.,Late The American Charles Francies Brush manufactured some carbon arcs.,The Inventor Thomas Edison experimented with thousands of different materials, eventually produced a bulb that could glow for over 1500 hours.,汉弗莱戴维爵士（法拉第的老师）,k电弧,manufactured,mnjfkt 制造，加工（manufacture的过去式）,carbon arcs电 碳弧,bulbblb 电灯泡,There are three kinds of light. 1.Incandescent lamp(白炽灯)： a.Incandescent lamp （白炽灯） b.Tungsten halogen lamp（卤钨灯） c.Halogen lamp （卤素灯） 2.High intensity discharge lamp-HID（气体放电灯） a.Fluorescent lamp （荧光灯） b.Sodium lamp （钠灯） c.Metal halide lamp （金属卤化物灯） 3.Others . a.Electrodeless Lamp（高频无极灯） b.Light Emitting Diode（发光二极管） ,In the early 19th century，a British chemist made the first arc lamp in the world by using 2000 cells(电池） and 2 carbon rods. But this kind of light is too strong，it cannot be used in the house but only in the street.,In 1879 By Thomas Edison-an American inventor The temperature of the filament: 3000 Average life span: 1000h Its a lamp which ranks first in the production of the world. But many countries are trying to stop using it, because of its heavy pollution.,Incandescent lamp（白炽灯）,filament flmnt 灯丝,life span 寿命,Compare to Incandescent lamp, this kind of lamp has longer life span(4000h) and higher light efficiency. It It is often used in the meeting room,the exhibition hall and the stage.,Tungsten Halogen Lamp（卤钨灯）,light efficiency 光效率,Fluorescent Lamp（荧光灯，俗称日光灯）,Long life span: 2500h3500h High light efficiency Good color rendering The temperature of the filament: 1000,color rendering显色性,Sodium Lamp (钠灯),The highest light efficiency. Fog permeability Life span: 20000h Be used in roads, airports, terminals, highways,etc.,Fog permeability 透雾性,Electrodeless Lamp（高频无极灯）,Very long life span: 40000h80000h Energy saving Brighter So,it is often used in some places which have higher requirements for safety . Such as tunnels, subway stations and factories.,tunnels 隧道,Light Emitting Diode（发光二极管）,Same features as electrodeless lamp, but more energy saving. It is secure when it work under the low thermal voltage. And its surface temperature less than 60.,low thermal voltage 低热电压,What will happen if our world have no light?,The ordinary light, it is a witness of human conquest of the night.,Thats all,thank you!,