evaluated in this issue a little-known both in optics and in quantum coherence of a source. As shown in the figure in the traditional double slit experiment is considered to be the source now is not only widespread but each point source emitter has a degree of inconsistency with his next. Then the condition for D1 and D2 slits are coherent emitters is that the length between them is less than the coherence length (1), then knowing the time of coherence of the source can find the volume of coherence (3). This is proportional to the inverse square of frequency, this is in line with everyday experience. Then the interference pattern is formed on the screen (4) depends on the time difference (5), which is the real part it can be approximated by (6). Where it appears the angular frequency of consistency (7).
As explained in the note, in the case of laser is very low because the coherence time of the source is high, eg in comparison with light sodium. If the frequency of consistency is great not be observed diffraction pattern on the screen.
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