The interplay between dust and radiation

The attenuation of radiation due to dust depends on the composition and optical properties of the dust grains. This is fundamental to determine the impact of radiation on chemical evolution. In this chapter, we discuss how we can compute grain properties such as the cross-sections for extinction, absorption and scattering, and the asymmetry parameter from their composition and size distribution. We then show how these properties can be used to calculate the attenuation of the photochemical rates by dust.