STUDY ON COHERENCE PROPERTIES OF LIGHT FIELDS INFLUENCED BY A MONOCHROMATOR

The effect of a single-and a double-grating monochromator on the coher ence properties of light fields is studied in detail experimentally by measuring the degree of coherence of the field at the entrance and ex it slits of a monochromator. It is found that the state of spatial (sp ectral) coherence of the light field incident at the entrance slit of a monochromator is modified considerably at the exit slits of a single and a double monochromator. The spectral degree of coherence (SDC) at the exit slit of a double monochromator is found to be more than the SDC at the exit slit of a single monochromator. It is therefore necess ary that, while synthesizing a secondary source at the exit slit of a monochromator, the coherence properties of the secondary source must b e carefully studied to analyse the far-field spectrum of such a source .