Nephelometer Flashcards
what is used to describe particle light scattering and backscattering?
integrating nephelometer
what is the total scattering angular range
7 to 170
how do we calibrate integrating nephelometer
we first use particle-free air and then CO2 with higher refractive index
what are the four unknown parameters in nephelometer calibration
calibration factor for scattering and backscattering; wall scattering for both also
what is the value of rayleigh backscattering coefficients compared to total scattering coefficient?
one half
what describes the spectral behavior of particle scattering?
angstrom exponent
what happens in absorption of light by a particle?
the energy of the photon is taken up by a paticle and it becomes heat
what does an absorption photometer do?
it is used to measure the particle light absorption coefficient and the particle mass concentration of black carbon
what are the ways to measure absorption coefficient
difference of extinction minus scattering, photo acoustic sensor, filter-based
what happens to relative uncertainty of absorption coefficient for low single scattering albedo?
lower uncertainty
when is the difference of extinction minus scattering effective?
it is most effective at high concentration and low ssa
why dont we use photo acoustic sensor?
it is sensitive to background noise and voc surrounding the aerosol can vaporize thus reducing the absorbed energy by the particle
what are the parts of filter-based absorption photometer?
light source, filter, detector
what causes the higher probability for a photon to be absorbed by particles?
the light path enhancement factor due to the multiple scattering by the filter
what are the different types of absorption photometer
particle soot absorption photometer, aethalometer, multi angle AP
