BIOL 2020 Chapter Notes - Chapter 6: Scattering, Geometric Standard Deviation, Coulter Counter
20 Apr 2020
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Document Summary
Laser light diffraction & dynamic laser light scattering: laser light diffraction: 1-1000um. Laser for larger particles; dynamic laser for very smaller particles. Dry/wet samples (aerosols, powder, suspensions, emulsions) broader applications. Particle must be larger than laser"s wavelength (632. 8nm) Detector receives signal from the fwd direction of incident light. Depending on particle size, scatter of light will vary. Large particles scatter light at narrow angles with high intensity. Small particles scatter at wider angles with low intensity. Larger the intensity of scatter light, larger the area. We can convert this area & volume to weight average diameter. We get 3 average diameter values: volume/weight/number average diameter: dynamic laser light scattering/ photon-correlation spectroscopy (dls)/(pcs): 0. 001-2um. Comparable to or smaller than lasers wavelength (632. 7nm) Detector is situated at incident angle from sample (90 degree) Governed by principles brownian motion of small particles; random motions/fluctuation change light pattern & scattering. Larger particles will not undergo brownian motion only smaller ones.
