. Carnegie Institution of Washington publication. ena were much the same,but far more brilliant. The arrows were now evenly wedge-shaped and veryslender. The fringes entered as nearly vertical hair-like striations, and, after cx L » 26 THE INTERFEROMETRY OF passing the optimum, vanished as inflated arrows. The range of visibilitywas, as before, about mm., so that the change of order has not had anyfurther marked effect, such as might be anticipated. As in the precedingparagraph, if the impinging collimated beam is narrowed, the range of visi-bility decreases; in fact, the arrows themselves
. Carnegie Institution of Washington publication. ena were much the same,but far more brilliant. The arrows were now evenly wedge-shaped and veryslender. The fringes entered as nearly vertical hair-like striations, and, after cx L » 26 THE INTERFEROMETRY OF passing the optimum, vanished as inflated arrows. The range of visibilitywas, as before, about mm., so that the change of order has not had anyfurther marked effect, such as might be anticipated. As in the precedingparagraph, if the impinging collimated beam is narrowed, the range of visi-bility decreases; in fact, the arrows themselves are reduced to slightly obliquelines. Within the limits given the fringes are well adapted for interferometry. First-order spectra are not available because of the large value of i in thecase of the right-angled prism. Taking the results of the last two paragraphs together, the increase of therange of displacement is due to the dispersion of the prism. The breadth ofthe pencil, diffracted at the slit, after leaving the collimator and prism, 12. 13 increases. It was shown in the earlier report that inversion of spectra on alongitudinal axis does not preclude the possibility of interference. Taken asa whole, therefore, the present results have a direct bearing on Huyghenssprinciple. 14. Prism methods without grating.—A more interesting method, in somerespects, in which the grating is entirely dispensed with, is shown in figure14. L is the beam of white light from a collimator, P a refracting prism (herewith a 60° prism angle), M and N the opaque mirrors, with either or bothon a micrometer, P a silvered reflecting prism (here right-angled). Thetelescope is at T and should have high magnification. The rays L are refractedinto a b c and a b c and the two spectra observed by the telescope at of the prisms should be on 3 adjustment screws, as well as the must be revolvable slightly around a vertical axis and capable of fore-and-aft motion. P is preferably a large
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