An interference pattern of two systems of fringes has beei obtained by using two radiations in a Hilgor prism interferometer. A system of White: baads with eqial spacing which are always parallel to the refracting edge of the prism is the result of the intersection of the two systens of fringes.The white bands travel as one of the reflecting mirror in the interferometer makes a parallel displacement. Let d be the displacement of mirror when tbe white bands travel one spacing, we have 1/λ2-1/λ1=1/2d. Two yellow doublets in sodium and mercury lamps were used. The values found for 1/λ2-1/λ1 were 17.22 cm-1 and 63.29 cm-1 respectively. A comparison of this method with the visibility curve by Michelson interfero-meter has been digcussed.
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