Essay Questions
- Using Figure 3 as a reference, provide a comprehensive discussion on the size-dependent dynamic properties of aerosol particles. Elaborate on at least four different properties shown in the figure (e.g., settling velocity, diffusion coefficient, relaxation time, electrical mobility), explaining the physical principles behind each and how they vary with particle diameter.
- Compare and contrast the two major categories of aerosol formation: nucleation and comminution. Discuss the typical size ranges, sources (as indicated in Figure 2), and subsequent atmospheric behavior (e.g., coagulation, settling) of particles generated by each process.
- Describe the principles of light scattering by aerosol particles. Explain how particle size relative to the wavelength of light (the parameter α) dictates the scattering regime (Rayleigh, Mie, geometrical optics) and how this phenomenon is utilized in optical methods for measuring aerosol particle size.
- Explain the process of measuring an aerosol’s size distribution using a cascade impactor. Describe the device’s principle of operation, the significance of the Stokes number, and discuss at least two challenges that must be considered to obtain an accurate measurement.
- Discuss the role of aerosols in atmospheric visibility. Define the extinction coefficient and visual range, and explain how they are related through the Koschmieder equation. Elaborate on how aerosol properties like concentration, size, and refractive index influence light extinction and, consequently, visibility.