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The term chiral describes an object, especially a molecule, which has or produces a non-superimposable mirror image of itself. In chemistry, such a molecule is called an ''enantiomer'' or is said to exhibit ''chirality'' or enantiomerism. The term "chiral" comes from the Greek word for the human hand, which itself exhibits such non-superimposeability of the left hand precisely over the right. Due to the opposition of the fingers and thumbs, no matter how the two hands are oriented, it is impossible for both hands to exactly coincide. Helices, chiral characteristics (properties), chiral media,〔 〕 order, and symmetry all relate to the concept of left- and right-handedness.〔Note: For more discussion regarding wave propagation and handedness see: Talk:Polarizer/Lengthy quotes〕 ==Wave propagation as handedness== Electromagnetic wave propagation as handedness is wave polarization and described in terms of helicity (occurs as a helix). Polarization of an electromagnetic wave is the property that describes the orientation, i.e., the time-varying, direction (vector), and amplitude of the electric field vector. For a depiction, see the image to the left. In the image, it can be seen that polarizations are described in terms of the figures traced as a function of time all along the electric field vector. A representation of the electric field, as a vector, is placed onto a fixed plane in space. The plane is perpendicular to the direction of propagation. In general, polarization ''is elliptical'' and is traced in a clockwise or counterclockwise sense, as viewed in the direction of propagation. If, however, the major and minor axes of the ellipse are equal, then the ''polarization is said to be circular '' . If the minor axis of the ellipse is zero, the polarization is said to be linear . Rotation of the electric vector in a clockwise sense is designated right-hand polarization, and rotation in a counterclockwise sense is designated left-hand polarization Mathematically, an elliptically polarized wave may be described as the vector sum of two waves of equal wavelength but unequal amplitude, and in quadrature (having their respective electric vectors at right angles and π/2 radians out of phase).〔Description of Polarization. Federal Standard-1037C. Aug 23 2000. Accessed on 2010-06-28.〕〔Wavelength is the distance between points of corresponding phase of two consecutive cycles of a wave. The wavelength, is related to the propagation velocity, v , and the frequency, f , by = v /f . (Federal Standard-1037C ) Aug 23, 2000. Accessed on 2010-06-28〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Chirality (electromagnetism)」の詳細全文を読む スポンサード リンク
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