What is a polarimeter and polarimeter experiments?

Polarimeter definition: 

Polarimeter apparatus:

A  polarimeter consists of a long tube with a side of flat glass, in which the sample is placed. On each side of the tube are a Nicole prism, one called a polarizer and the other an analyzer. The polarizer is kept stationary and converts monochromatic light into a plane-polarized beam. The angle of rotation of a flat polarized beam is measured by passing a monochromatic light through a polarizer. This beam is rotated as it passes through a sample already filled in a polarimeter tube.

Samples are usually prepared as a solution where optically active substances are dissolved in optically inert chemicals such as distilled water or methanol. After passing the sample the analyzer is rotated manually. When the analyzer is rotated at an appropriate angle, the maximum amount of light travels to the detector (telescope) and shines. 

Polarimeter principle:

The principle of polarimeter set-up consists of polarimeter light source (S), polarizer (P), analyzer (A) with angle measuring scale, and eyepiece (E).

                          Polarimeter experiment / polarimeter diagram

Two Nicole prisms are placed between the monochromatic light source, S (usually sodium lamp), and the eyepiece. Light undergoes polarization and the plane becomes polarized (vibrations are limited to one plane only). This plane-polarized light then reaches the eye through a second Nicole Prism, the A analyzer. The visual field is observed through a telescope eyepiece (E).

However, when the axis of the analyzer is perpendicular to the axis of the polarizer, no light reaches the eye. The polarizer and the analyzer are arranged according to the lack of light. Eyes A tube filled with sugarcane sugar solution is placed between two prisms. Some light can now be seen through a telescope eyepiece. The analyzer should be rotated so that the light does not reach the eyes once again.

Now some light can be seen when the sugar solution was placed between the prisms whose axes were perpendicular to each other and no light was initially visible. So what made this light visible on the other side when neither of the two prisms was moved? Light is visible only if the plane of polarization is rotated in any way. 

Polarimeter for sugar analysis

In this way, the plane of polarization must be rotated by a solution of sugarcane sugar.

Polarimeter application

 A polarimeter is widely used in the food, chemical and pharmaceutical industries for quality control, process control, and research. The most famous application is the analysis of Sugar using the International Chinese Scale °Z.

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