Propagation through random distributions of spheres

Part I Theory, and Design of "Macroscopic Gas" A general theory for propagation through random distributions of arbitrary objects is applied to treat "gases" of spheres large compared to wavelength. In order to use microwaves to determine the range of applicability of the theory, and to facilitate its extension to "dense gases" and "liquids", a "compressible macroscopic gas" was engineered: turbulent air streams and collision processes provide the "randomness" in volume distributions of spheres. Statistical information required for interpreting microwave measurements is obtained from movie films. Part II Design of Range, and Experimental Data A 5-millimeter range for measuring scattering from extended random distributions of objects is described, and data on random volume distributions of several types of spherical scatterers are given. The time-average energy loss and the time-average phase shift of the coherent wave transmitted through the distribution are initially linearly proportional to the number of scatterers: with increasing concentration of scatterers the slopes of the attenuation and phase curves decrease, showing packing effects. The magnitude of the incoherent transmitted wave is also given.