1. Light Scattering Biophysics

2. Single Particle Rough Treatment
Sample - dipole
Light Source k0 q
The scattering angle, q, is defined w/r transmitted light in the scattering plane. The scattering plane is defined by the vectors k and k0.
P is the polarization which is the total dipole moment/volume. a is the polarizability.
Go over description of light in terms of 3d exponential function (board).

3. Single Particle Rough Treatment Bottom line
Light can be described by electric field
For Horizontally polarized light intensity the |E|2 given by
For vertically polarized light
For unpolarized light
Why is there angular dependence for one but not the other?
Why does the sky usually appear blue?

5. But you asked why our mountains-which are made up of many colors-appear blue. The blue-sky principle still holds: when you view a dark, solid object, such as a mountain, from a distance, the scattered light makes it appear blue. Yet the distinct blue haze of the Appalachians can also be attributed to the thick vegetation that blankets the slopes. Tiny hydrocarbon particles, including terpenes from pine trees, are released by plants. The particles react with natural ozone molecules to produce a hazy effect over the mountains. Again, the small size of the particles means that the light scatters blue. The Blue Ridge is not unique in this respect. This effect occurs in other mountain ranges around the world, including the Blue Mountains in Australia.

6. Dilute gas of small particles
Use Classius-Mosotti relation to express polarizability a in terms of index of refraction, n. n2 – 1 = 4pNa,
Scattered light per unit volume goes as molecular weight

7. Macromolecules in solution
n2 – 1  n2 – no2, where no is the index of refraction of the medium.
Rq = KcM, with
With small interaction get
Kc/ Rq = 1/M + 2Bc where B = 2nd virial coefficient – fudge factor.
Rq = Rayleigh ratio =

8. Large macromolecules Mostly Forward Scattering
Get molecular weight and size
Zimm plot

9. Nephelometer

10. Raw Data Why plot as Log(sin(angle)? Why buffer give more noise?
What do you notice about angular dependence?

11. Data from Chen et al BJ 2004