An Experimental Study of the Change in Phase Accompanying Reflection of Light from Thin Evaporated Films

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The phase change accompanying reflection from thin evaporated films was measured for three different cases: first, front surface deposits of silver on glass; second, back surface deposits of silver and gold on glass; and third, front surface deposits of dielectrics on nearly opaque silver layers. In all three cases the phase change was determined as a function of the thickness of the deposit. When the deposits exceeded several hundred angstroms the results were consistent with boundary value solutions of the equations of electromagnetic theory but for thinner deposits they are explained by light scattering rather than reflection from uniform layers. From index of refraction determinations it was found that films of cryolite and MgF2 were non-porous but that CaF2 was highly porous. Very thin films of ZnS showed density anomalies.