Saturday, 24 April 2010

Laurent’s Half-Shade Polarimeter

Principle


It is used for the measurement of the angle of rotation of optically active substance in solution. That is, angle through which the plane of the polarized light is rotated on passing through a specific length of solution of known concentration.

General Description


The experimental arrangement is shown if figure, S is source of monochromatic light placed at the focus of convex lens L. The beam, rendered parallel by lens L, falls on called polarizer P. After passing through polarizer P the light become plane polarized. The polarized light beam passes through a half-shale device H (called Laurent plate) and then through a tube T containing optically active solution. The transmitted light passes through another Nicol ‘A’ which can be rotated about the direction of propagation of light as axis and its rotation can be read on a circular scale graduated in degree, with the help of a Vernier.
Half shade polarimeter

Bi-quartz polarimeter


  • It is consists of bi-quartz plate of Lauren’s half shade plate.
  • White light is used in place of monochromatic light.
The left half plate rotates the plane of vibration in anti – clockwise direction, while right-half plate in the anticlockwise direction.

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