. Carnegie Institution of Washington publication. 5/2, these become TABLE 3. SeXio6 Diff. + cm. + 42+ -23 The maximum error of 4X icr7 cm. is equivalent to but a little over i per centof the distance between fringes, and it would be idle to suppose that the appa-ratus, figure 4, could be set more accurately. In fact, the largest error occursin the second set, which were first made and in which the play of the apparatuswas inadequately smooth. 6. Theory.—Hence the theory of the apparatus (fig. 6) may be regardedas justified. Here the rays Y and V come from the first grat
. Carnegie Institution of Washington publication. 5/2, these become TABLE 3. SeXio6 Diff. + cm. + 42+ -23 The maximum error of 4X icr7 cm. is equivalent to but a little over i per centof the distance between fringes, and it would be idle to suppose that the appa-ratus, figure 4, could be set more accurately. In fact, the largest error occursin the second set, which were first made and in which the play of the apparatuswas inadequately smooth. 6. Theory.—Hence the theory of the apparatus (fig. 6) may be regardedas justified. Here the rays Y and V come from the first grating (G transmit-ting), and after reflection from the opaque mirrors M and N (the former ona micrometer) impinge on the second reflecting grating G, with a smaller REVERSED AND NON-REVERSED SPECTRA. 15 grating space, and thereafter interfere along the line T, entering the treat the case the mirrors M, etc., may be rotated on the axis T normal toG in the position M\. Gn and Gm show the reflections of G in the mirrors \ //^s? /kjfa \. AT and MI. We thus have a case resembling the interferences of thin plates,and if em is the normal distance apart of the mirrors M\ and N, the displace-ment Aem per fringe is given by X = 2Atfm COS 6/2 where 5 is the angle between the rays incident and reflected at the is the equation used above. If the mirrors and the reflections of thegratings G make angles a/ 2 and a with G, the actual lengths of the rays (pro-longed) before meeting to interfere terminate in e and f respectively. Let theimage of G be at a normal distance e apart. Then e — zem cos 0/2 , for the figurefdbs is a parallelogram. If the distance eg is called C we may also write X = e cos 8t-\-C sin 62since C = 2em sin <r/2 and the angle of diffraction fl»=( 7. Compensator measurements. Sharp wedge. — With the object of testingthe interferometer under a variety of conditions, measurements were madewith a number of different compensators and the experie
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