Half shade polarimeter is very sensitive for those persons who are suffering from colour blindness. It is only suitable for a particular wavelength since the quartz. ObjectiveTo determine the specific rotation of sugar solution-using Bi-quartz Polarimeter. Apparatus RequiredBi-quartz Polarimeter, light source, a glass tube. Two types of polarimeters are generally used in the laboratory now a days: (a) Laurent's Half Shade Polarimeter. (b) Biquartz Polarimeter. Laurent's Half.
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Now the tube is filled with optically biquartz polarimeter solution and it is set in its proper position. The optically active solution rotates the plane biquartz polarimeter polarization of the light emerging out of the polariser P by some angle.
So the light is transmitted by analyzer A and the field of view of telescope becomes biquartz polarimeter. Now the analyzer is rotated by a finite angle so that the field of view of telescope again become dark.
This will happen only when the analyzer is rotated by the same angle by which plane of polarization of light is rotated by optically active solution.
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The position of analyzer is again noted. The difference of the two readings will give you angle of rotation of plane of polarization 8.
A difficulty is faced in the above procedure that when analyzer is rotated for the total darkness, then it is attained gradually and hence it is difficult to find the exact position correctly for which complete darkness is obtained.
To overcome above biquartz polarimeter half-shade device is introduced between polariser P biquartz polarimeter glass tube T. One half ACB is made of glass while other half is made of quartz.
What is Biquartz polarimeter? - Quora
Both the halves are cemented together. The quartz is cut parallel to the optic axis. The thickness of the glass is selected in such a way that it absorbs the same amount of light as is absorbed by quartz half. Biquartz polarimeter us consider that the vibration of polarisation is along OP.
On biquartz polarimeter through the glass half the vibrations remain along OP.
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The O-component travels faster in quartz and hence biquartz polarimeter emergence 0-component will be along OD instead of along OC. Now if the Principal plane of the analyzing Nicol is parallel to OP biquartz polarimeter the light will pass through glass half unobstructed.
The O-component travels faster in quartz and hence an emergence 0-component will be along OD instead of along OC.
Biquartz polarimeter if the Principal plane of the analyzing Nicol is parallel to OP then the light will pass through glass half unobstructed. Hence glass half will be brighter than quartz half or we can say that glass half will be bright and biquartz polarimeter quartz half will be dark.
When the principal plane of analyzer is along Biquartz polarimeter then both halves will be equally bright. On the other hand if the principal plane of analyzer is along DOC.
Thus it is clear that if the analyzing Nicol is slightly disturbed from DOC then one half becomes brighter than the other.
biquartz polarimeter Hence by using half shade device, one can measure angle of rotation more accurately. Determination of Specific Rotation In order to determine specific rotation of an optically active substance say sugar the polarimeter tube T is first filled with pure water and analyzer is adjusted for equal darkness Both the halves should be equally dark biquartz polarimeter.
The position of the analyzer is noted with the help of scale.