function [flag_R,x,y,angle_rad,phi_out,phi_prim] = g_snell(angle_rad_in,phi_in,n1,n2,r1,r2)

flag_R = 1;
phi_prim=asin((n1/n2)*sin(phi_in));
phi_out=asin((r1/r2)*sin(phi_prim));

if (isreal(phi_out) == 1)
   
   if ( r1 == r2 )
      alpha=pi-phi_prim-phi_out;
   else
      alpha=phi_out-phi_prim;
   end
   
      
   angle_rad = angle_rad_in + alpha;

   x=r2*cos(angle_rad);
   y=r2*sin(angle_rad);
   
else
   flag_R=0;
   angle_rad = angle_rad_in;
   x=r2*cos(angle_rad_in);
   y=r2*sin(angle_rad_in);   
end