Cet article est une ébauche concernant l’électromagnétisme. La permittivité du vide, permittivité diélectrique du vide ou encore constante électrique est une physique eugene hecht pdf physique. Eugène Hecht, dans son livre “Optique”, nous donne cette interprétation: ” De façon conceptuelle, la permittivité représente donc le comportement électrique du milieu.

Rechercher les pages comportant ce texte. La dernière modification de cette page a été faite le 7 novembre 2017 à 17:49. Not to be confused with circularly polarized light. Optical activity is measured using a polarized source and polarimeter.

This is a tool particularly used in the sugar industry to measure the sugar concentration of syrup, and generally in chemistry to measure the concentration or enantiomeric ratio of chiral molecules in solution. The two asymmetric crystal forms, dextrorotatory and levorotatory, of tartaric acid. The rotation of the orientation of linearly polarized light was first observed in 1811 in quartz by French physicist François Jean Dominique Arago. In 1849, Louis Pasteur resolved a problem concerning the nature of tartaric acid. In order to display optical activity, a fluid must contain only one, or a preponderance of one, stereoisomer. At the fundamental level, optical activity is a case of circular birefringence, and can best be understood in that way. 90 degree phase shift between the x and y components that we have decomposed each circular polarization into.

Sucrose solution concentration measuring experiment, demonstrating optical rotation. For a pure substance in solution, if the color and path length are fixed and the specific rotation is known, the observed rotation can be used to calculate the concentration. This usage makes a polarimeter a tool of great importance to those trading in or using sugar syrups in bulk. In the presence of an applied magnetic field, it is possible for samples of all compounds to exhibit optical activity. A magnetic field aligned in the direction of light propagating through a material will cause the rotation of the plane of linear polarization. This Faraday effect is one of the first discoveries of the relationship between light and electromagnetic effects.