function y=b_integral(theta,lambda,D)
%
% 2005.12
% Emmanuel Boss
% emmanuel.boss@maine.edu
% School of Marine Sciences, University of Maine, USA
%
% Calculates an ingrand needed to perform backscattering computation using Wetlabs 
% Eco-type backscattering sensors.
%
%
% INPUT
% Incident wave wavenumber                      (lambda) [nm] 
% Sphere diameter                               (D)     [m] 
% scattering angle                              (theta)    [degree]
% Center angle for backscattering               (nominal_angle)    [degree]

% OUTPUT
% integrand value                               (y)


[beta,Qb]=beta_theta(lambda*10^-9,D,theta);
y=W1(lambda).*N_sphere(D).*Qb*pi.*D.^2/4;

