Light exhibits a "wavy" quality, in which it oscillates as it moves along.
When this wavy light passes through a substance, a phenomenon
occurs wherein the direction of the undulating, wavy light rotates.
This is the optical rotation of light.
Using this as a basis, let's try to explain optical rotation with an easy
to understand, metaphorical illustration. Draw a wavy line on a long
piece of paper. Hold the center of both ends of the piece of paper
firmly with your fingers. Turn it around at all sorts of angles. This
oscillating wave that moves in the direction of many angles, which
is a deeply complicated phenomenon entangled with other matter is
natural light. It is the normal state of light.
The angle of rotation of light can't be measured in this state. The oscillating waves of light move at each and every angle, so it is impossible to determine which wave passes through a substance and to what degree it rotated.
travels along must be limited to move in the direction of one angle. In order to achieve this, light is passed through something called a "polarizer." A polarizer has a grid-like pattern, arranged in an intricate, alternating fashion of lines that light does not pass through and spaces that light passes though. The light is obstructed by the polarizer which enables only a single wave of light moving at one angle to pass through. This is called "polarized light."
By rotating the polarizer (the second polarizer in a polarimeter is called an "analyzer") and finding the angle at which the polarized light passed through, or the angle at which it was blocked, it is possible to measure the angle at which the light passed through a substance (the angle of rotation). Polarimeters use this principle to measure the angle of rotation of a substance.
Polarimeters are instruments used for measuring the angle of optical
rotation of light. General polarimeters contain mechanisms such as a
light source and polarizer. Light emitted from the light source passes
through the polarizer and the angle of the wave of light is restricted.
The angle at which the light rotates is measured when it passes
through the substance.
During measurement, if the plane of vibration which faces the light
source appears to be rotating clockwise, it is dextrorotatory. If it
appears to rotate counter-clockwise, it is levorotatory. "Dextrorotatory"
comes from the Latin word "dextro" meaning, "right." "d-rotary" can
also be used to refer to dextrorotatory. "Levorotatory" comes from
the Latin word "levo" meaning, "left." Levorotatory is also known as
"l-rotatory. The system for denoting optical isomers (enantiomers),
either d- or l-, is derived from these words.
Polarimeters are largely used in the sugar refining and pharmaceutical
industries. In the sugar refining industry, polarimeters are used to
determine the type of sugar or to ascertain the purity. In the world of
pharmaceuticals, there are many cases where chemical compounds
may be subjected to certain standards, depending on the angle
of rotation. Polarimeters are used to perform checks such as
determining the type of substance.
In regards to polarimeters, when it comes to the optical rotation of light, "polarizers" sound like a difficult concept that's hard to imagine. However, polarizers are surprisingly used in various places throughout everyday life.
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