. Light, a textbook for students who have had one year of physics. IZD id ~z> 122 LIGHT The desired result, making the maxima narrow, sharp andbright, can be secured by getting interference from more thantwo points at once. For instance, if Fresnels mirror experi-ment could he arranged so that there were three regularlyspaced apparent sources of light, instead of only the two, SL>. the maxima would be sharper and brighter,—if therewere four, they would be still sharper,—and so on; but oneof the best devices for the purpose is what is called a grating. In its theoretically simplest
. Light, a textbook for students who have had one year of physics. IZD id ~z> 122 LIGHT The desired result, making the maxima narrow, sharp andbright, can be secured by getting interference from more thantwo points at once. For instance, if Fresnels mirror experi-ment could he arranged so that there were three regularlyspaced apparent sources of light, instead of only the two, SL>. the maxima would be sharper and brighter,—if therewere four, they would be still sharper,—and so on; but oneof the best devices for the purpose is what is called a grating. In its theoretically simplest form, a grating is an opaqueplate containing a large number of slits, parallel and spacedclose together at equal intervals. Light from a narrow source,like a distant slit, or a star, falls upon it and passes throughthe many narrow slits, producing interference bands on theother side. Let AB, figure 66, represent a section of such a.
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectlight, bookyear1921
