# Exercise 5.2.5 Rayleigh Scattering

| 1. Generate some numbers for scattering cross sections using the equations given.
|  | Look, e.g., at "air" molecules including some water vapor or ozone as scatterers, and wave lengths from the IR to the UV.
| 2. Derive or justify the equation lsc = 1/n s. Show that for air we get lsc (=) 160 · l4 if we give l in km and l in µm.
|  | Hint 1: Consider the particle to be a cube with s being the area of a face. All light will be scattered if the total area of those cubes projected on a surface perpendicular to the light beam covers that area completely. lsc then is the length of a cube that contains enough particle to meet that condition. Hint 2: The volume of an air "molecule" can be estimated from the fact the liquid air has about the same density as water.
| 3. Generate some numbers for penetration depths in air. How thick does an ozone (O3) layer with a density nOz = 8 ml/m3 have to be to absorb most of the incoming ultraviolet radiation (especially "UV-B"; l » 300 nm)
| Link to the solution

With frame

5.2.5 Not so Perfect Materials

Solution to 5.2-3: Attenuation of Light

Solution to Exercise 5.2-3: Rayleight Scattering

© H. Föll (Advanced Materials B, part 1 - script)