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[Display omitted] • Molecular polarizability density governs the magnitude of refractive index. • Aromaticity determines the refractive index dispersion. • Aliphatic cations and alkyl chains have weak influence in dispersion. • Aromatic cations produce high refractive index dispersion at short wavelengths. • Absorption bands related to π orbitals explain the dispersion in aromatic cations. In this work, we study the contributions that different molecular blocks have in the wavelength-dependence of the refractive index in ionic liquids. The ionic liquids chosen for this work are combinations of the bis(trifluoromethylsulfonyl)imide anion with cations based on four different heterocycles with different extents of charge delocalization. The analysis is performed in terms of the experimental electronic polarizability, which is obtained by combining measurements of refractive index curves and densities via the Lorentz-Lorenz equation. Exploiting the additivity of electronic polarizability in ionic liquids, the contribution of the anion and the heterocycles of the cations is separated from that of the alkyl chains. Our results show important differences in these contributions, revealing a key influence of the charge delocalization in the cationic rings on the behavior of the refractive index dispersion. The understanding of how different parts of ionic liquids affect their refractive index dependence on wavelength would allow to gain precise control of this magnitude, enabling the development of customized optical materials for diverse applications in photonics and sensing technologies. [ABSTRACT FROM AUTHOR]

In this paper, we discuss a demonstration we have been performing for years with students from different levels, from physics students from our university to high school students in some talks aimed at encouraging them to study science. It provides visualization of Brewster's angle in an ingenious way using a "loaded" liquid crystal display (LCD) monitor lacking its front polarizing filter. The demonstration is based on observing the hidden image of this loaded LCD reflected in a transparent plate. In some way, we deal with a reverse version of what happens when a vampire faces a mirror and sees no reflected image of himself. [ABSTRACT FROM AUTHOR]

• A deep analysis of measurement accuracy in dispersion measurement by RISBI is presented. • Both, refractive and group index measurement are evaluated. • Assessment of the different contribution of refractive and group refractive index uncertainty is carry out. • It is shown that uncertainties better than 10−4 can be achieved. Uncertainties of refractive and group index in dispersion measurement by spectrally resolved white light interferometry are deeply analyzed. First, the contribution to uncertainty of the different parameters affecting both indices is identified. Afterwards, results are presented for a 1.5 mm thick fused silica sample over a broad spectral range, from 400 to 1000 nm, and the effects that mostly deteriorate the measurement accuracy are established. Finally, the different contributions are quadratically combined to determine the total uncertainty of the two indices. [ABSTRACT FROM AUTHOR]