Light; a course of experimental optics, chiefly with the lantern . Fig. 99.—Newtons Rings with Flat Glasses. J-inch thick, or, at least, one must be so), and having care-fully cleaned them, place a ring of gold-leaf between themat their circumference. Mounted as in Fig. 99, pressurefrom the centre screw at the back produces, as in the othercase, Newtons rings, which, in either case, are presentedto the lantern and focused on the screen precisely in the IX.] NEWTONS RINGS. 167 manner of the soap-film (Fig. 97). This method is withinthe power of many who like to construct their ownapparatus. It
Light; a course of experimental optics, chiefly with the lantern . Fig. 99.—Newtons Rings with Flat Glasses. J-inch thick, or, at least, one must be so), and having care-fully cleaned them, place a ring of gold-leaf between themat their circumference. Mounted as in Fig. 99, pressurefrom the centre screw at the back produces, as in the othercase, Newtons rings, which, in either case, are presentedto the lantern and focused on the screen precisely in the IX.] NEWTONS RINGS. 167 manner of the soap-film (Fig. 97). This method is withinthe power of many who like to construct their ownapparatus. It is clear that, knowing either the curve of the lens, orthe thickness of the gold-leaf, it is very easy to calculate. Fig. 100.—Newtons Rings, the thickness of the film of air at any given distance fromthe centre. Newton found that when he employed pure mono-:hromatic light, he obtained recurring rings of coloured light,or of darkness, as in a, b, c, d, e, f. Fig. 100, at once, twice,:hrice, and other multiples of one definite small soon discovered another beautiful fact, viz., that the rings il58 LIGHT. [chap. were broader, or required a thicker film, in red light thanin blue light; and finally, by a movable prism, he threwthe successive colours of the spectrum on the rings, andfound them gradually contract as he travelled towards theviolet end. With most lanterns there is hardly light enoughto employ this beautiful method; but the phenomena maybe shown as follows:—Arrange the Newtons rings, andfocus on the screen as before. Provide one of the movableslide-frames now used by all lantern lecturers, and fit in ittwo half-size glasses, one blue and one red. Condense thefull light on th
Size: 1593px × 1569px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1880, bookidcu3192403121, bookyear1882
