function n=ref_dust(lambda)
% The complex refractive index of dust based on OPAC/GADA data base
% input:
%      lambda in [um]
% output:
%      n - complex refractive index
load refdust.dat
m=interp1(refdust(:,1),refdust(:,2),lambda);
k=interp1(refdust(:,1),refdust(:,3),lambda);
n=m+i*k;
