a.PM2.5 is a criteria pollutant that can have immense impact toour health and visibility. It is defined using the aerodynamicdiameter. But how is this diameter being defined, i.e. what is thedefinition of aerodynamic diameter?
b. Why is PM2.5 defined using aerodynamic diameter?
c. What is the physical meaning of relaxation time of anatmospheric particle? And explain how the relaxation time isassociated with the size of the particles.
d. Impactor and cyclone are commonly used size-selection devicesto separate PM2.5 particles from the particle-laden air. Describewith sketches by hands to illustrate how the separation is achievedwith the impactor. Please define relaxation time and explain howthe particles separated with an impactor using the relaxation timeconcept. Be reminded to label the sketches clearly.
