dichroismu

Dichroism is an optical phenomenon observed in certain materials where they absorb different amounts of light depending on the polarization direction of the light. This means that when linearly polarized light passes through a dichroic material, its intensity is reduced more significantly if the polarization is aligned with one axis of the material compared to when it is aligned with another axis. This effect is dependent on the wavelength of the light, meaning a material might be dichroic at one wavelength but not at another.

The cause of dichroism lies in the anisotropic structure of the material. This anisotropy can arise from the arrangement of molecules within the material or from the presence of specific elongated chromophores. These structures interact differently with the electric field component of polarized light. If the electric field vector of the light is parallel to certain molecular axes or chromophore orientations, it can induce stronger absorption than if it is perpendicular.

A common application of dichroism is in the creation of polarizing filters. Dichroic sheets, often made from stretched polymer films containing aligned iodine molecules or other dichroic dyes, are used to absorb light polarized in one direction while transmitting light polarized in the perpendicular direction. This principle is fundamental to how liquid crystal displays (LCDs) function, where dichroic polarizers are used to control the passage of light and create images. The term "dichroism" itself comes from the Greek words "di" meaning "two" and "chroma" meaning "color," referring to the observation of two different colors or absorption levels depending on the orientation.