Re: scattering

Borgnino wrote:

Hi,

I would be grateful if someone could provide me with some references or insights on the following problem.

Consider a Gaussian beam entering a scattering media.
The scatter is due for instance to droplets that all have the same size, their size is much larger than the wavelength and they are distributed homogenously. The index of the droplets is slightly different than the propagation media.
The intensity profile on a screen at a distance z is partly determined by the size and distribution of the droplets.

Is there a simple way to know how this scatter will affect the intensity profile ?

For instance in free space I could just convoluate by a Fresnel kernel, or if my beam would go through an optical system I could use the PSF of this system.

Since the problem seems simple I've thought there must be a way to evaluate rapidly what would be roughly the intensity profile without heavy calculus but I can not find anything like this.

This is a common situation. A simple web search on "dynamic light scattering" will turn up all kinds of things. The standard book is written by Bohren and Huffman. One way to approximate is that the fluctations in number density of the particles will produce the scattering signal. Another is that the angle of the scattered light is proportional to a particular timescale of particle motion (forward equal slow, bacscatter equals fast).

There is no "intensity profile". One looks at cross-correlations and autocorrelations of the scattered light.

--
Andrew Resnick, Ph.D.
Department of Physiology and Biophysics
Case Western Reserve University
.