Molecular aggregation in optical glasses as revealed by light-scattering

Abstract

Sir C. V. Raman's new technique for the study of light-scattering based on the use of a Babinet compensator, has been successfully applied for the detection of the anomalous depolarisation in optical glasses. Thus the existence of the reversal of polarisation when the incident beam is polarised with vibrations horizontal, has been definitely established by the new method which is of an objective character. The present investigation further reveals that in glasses the scattered light is elliptically polarised when the incident beam is linearly polarised in a direction oblique to the scattering plane. These observations support the view that molecular aggregates do exist in glasses. One important point which emerges out of the present investigation is that those glasses which give larger values of Δρ_u exhibit elliptic polarisation to a correspondingly larger extent. Δρ_u is the difference between the observed value of ρ_u and the anisotropic part of ρ_u which can be considered to be equal to 2ρ_v/(1+ρ_v). It has been pointed out that for making comparative estimates of the sizes of particles in any two scattering media a knowledge of the values of Δρ_u in the two cases is by far more important than the corresponding values of ρ_h.