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May 30, 2011
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If I had a plane polarized light source on one side of a beaker of optically active substance, and a mirror on the other, light would go through the beaker and rotate. It'd hit the mirror and reflect back. On its way back through the beaker would the light rotate further, or rotate back to its original orientation?


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Jul 9, 2011
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It should rotate further.

Optically active solutions don't discriminate by direction. left, right, up down, forward, backwards... if the rotation is by + 30%, it will be by +30%.


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Dec 1, 2011
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Agreed. If the optically active compound rotates light 30 deg clockwise, for example, it will rotate something 30 deg clockwise no matter which way the light approaches from.
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Dec 30, 2009
Where the rain grows
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Another way to think about it - the amount of rotation is proportional to the thickness of the optically active material. Going back and forth through it means twice as thick, so it will rotate it another 30 degrees.
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