hi, i really confused about this two term. As i read from a book, ' in the Young's double slits experiment of light, if the time difference (that resulted from the path difference because of the two slits) is longer than the duration of each 'burst' (the photon),the received waves must come from different 'burst', which are unrelated and incoherent.' i want to know if 'coherent time' = duration of the 'burst' (about nanosecond for white light). if they are equal, i can understanding the above statement. if they are not, can anyone explain clearly, in detail to me ? Thank you very very much!