582 ON THE LIGHT EMITTED FROM A RANDOM DISTRIBUTION ETC. [436
and in like manner
so that this factor disappears. Continuing the process, we get approximately f!coa(0s-_01)d0ld02+f[d01d0i, ...
as when there were only two phases to be regarded.
Accordingly, the expectation of intensity for n phases is
?i{l-(n- l)8/7r}, ........ ...... .............. (44)
less than when Sf=0, as was to be expected, since the cases excluded are specially favourable. But in order that this formula may be applicable, not merely 8, but also nS, must be small relatively to 27r.
A similar calculation is admissible when the whole range is 2m7r, instead of 2-7T, where in is an integer.s very small.