Topics - Raleigh Scattering
If a strong beam of light is passed through a transparent, gaseous, or liquid medium containing solid or liquid particles, or even molecules of extremely high molecular weight, the light is scattered away from the direction of its incident path. The scattering is due to interference effects that arise from the density fluctuations in the scattering medium (i.e. the presence of particles or very high molecular weight molecules). There are two types of light scattering; one in which the wavelength of the scattered light differs from that of the incident light and that is called Raman Scattering
; the other is when the scattered light has the same wavelength as the incident light and this scattering process is called Raleigh Scattering
. In Raleigh scattering, the intensity of the scattered light is proportional to the product of the intensity of the incident light, an attenuation constant, a function of the refractive index and the Raleigh Constant. Now the Raleigh constant is a somewhat involved function of the molecular weight of the scattering substance, and so, a measurement of the intensity of the scattered light can give a value for the molecular weight. The scattering phenomena is used in a number of liquid chromatography detectors.