This paper is a complement to an earlier paper [Jpn. J. Appl. Phys. 35 (199
6) 4793] on the transmissivity of beams in multicomponent mixed materials o
f identical grain size and presents an analytical expression of transmissiv
ity based on the finite Markov chain in the case of mixed materials of diff
erent grain sizes. The expression is represented by the flux vector and the
response matrix obtained from the transition matrix.