Optical rotation is the rotational change of linearly
polarized light of a given wavelength as it travels
through certain substances. To understand this, light is
composed of vibrating waves. Normally, light waves
vibrate in all planes that are perpendicular to the
direction of where they transmit from. Perpendicular
means a straight line at right angles to another line.
A good example would be the lines forming the letter "L." Thus, if light was being
transmitted from left to right, it would vibrate up and down perpendicularly.
However, if light passes through certain materials (such as Polaroid plastic film) it would
selectively generate light waves that only vibrate in planes that run parallel (side by side
without touching) to one another. Thus, if the light was being transmitted from left to right,
it would vibrate in a vertical direction as well. Light that vibrates only in parallel planes is
said to be plane polarized, vertically polarized, or linearly polarized. In optical rotation,
when polarized light passes through a certain type of substance, it will emerge in a
different rotation. Optical rotation is measured in chemistry with a device known as a
polarimeter. Optical rotation is known to occur when light passes through certain sugar
solutions. This is why it is used by sugar companies to measure the concentration of
syrup. It is also being used in the field of medicine to measure the amount of sugar in the
blood in people with diabetes mellitus. Diabetes mellitus is a medical condition in which
the body is not able to effectively use a natural chemical called insulin.
Insulin's main job is to quickly absorb glucose (a type of sugar) from the blood into cells for their energy
needs and into the fat and liver (a large organ that performs many chemical tasks) cells for storage.
Optical rotation is also known as optical activity. Optical rotation comes from the Greek word "optikos"
meaning "eye" and the Latin word “rotationem” meaning “revolve.” Put the words together and you get