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Abstract It ie the purpose of thie note to show that the fluctuatione in the inetmtaneoue inbnaities at two arbitrary pointa in a stationery optical field am in general correlated and that thie oorrelation is proportional to the square of the coherence function introduced into the theory of partidy coherent fielda by Blanc‐Lapiem and Dumontet (1965) and independently by Wolf (1966). The reeult has a beering on recent experi‐menta by Hanbury Brown and Twies (1966) in whioh fluotuationa in the current output from two photoelectric cells eituated cloee to each other and illuminated by an ahat oohemnt beam of light were found to be comlated.
E. Wolf (Fri,) studied this question.