Optical Activity

A material which rotates the plane of incident linearly polarized light is said to be optically active. Viewing the light head-on, some substances rotate the electric field clockwise (dextrorotatory) and some produce a counterclockwise rotation (levorotatory). The property was discovered in quartz in 1811 by Arago. Two different crystalline structures of quartz produce d-rotatory and l-rotatory behavior. The two crystalline forms are said to be enantiomorphs of each other. The optical activity of quartz is associated with its crystal structure, as evidenced by the fact that neither molten quartz or fused quartz demonstrate optical activity.

一种能使入射线偏振光的平面发生旋转的物质被称为光学活性的。当正对光线观察时，某些物质会使电场顺时针旋转（右旋），而另一些物质则产生逆时针旋转（左旋）。这一性质于1811年在石英中被发现，由阿雷戈发现。石英的两种不同晶体结构会产生d-旋光性和l-旋光性行为。这两种晶体形式被称为彼此的对映体。石英的光学活性与其晶体结构有关，这一点得到了证明，因为熔融石英或熔融石英均不表现出光学活性。

In the case of many naturally occurring organic compounds such as sugar, tartaric acid and turpentine, optical activity is exhibited in the liquid state. This shows that the activity is associated with the individual molecules themselves.

在许多天然存在的有机化合物（如糖、 tartaric 酸和松香）中，光学活性在液态下表现出来。这表明光学活性与单个分子本身有关。