Finding the Index of Refraction of Gel



•Mag lite (or any lamp/lens combination which produces collimated (straight) light)

•1 m long measuring (2)

(or one 2 m stick)

•Polarizer (1)

•Ring stands (2)



Experimental setup for measuring the Brewster’s angle of a gel sample

  1. Make a brick-like gel sample
  2. Secure the lamp and the polarizer such that they’re held in place. 
  3.  Make sure that the rays from the lamp, the sample, and the polarizer lens all lie along the same plane.
  1. Move your head up and down until you see the most glare.  Keeping your head at this position, perform the next steps.
  1. Without misaligning the polarizer, move it vertically until you can see the sample through it (without moving your head).  Now rotate the polarizer until you remove the maximum amount of glare possible.  Take a qualitative note of the amount of light removed.
  2. Move the sample, and repeat steps 4 and 5 until you find the position at which the polarizer removes the maximum amount of light from the surface of the gel.
  3. Calculate n2 from the tangent of θB.

For a more detailed version, click here (instructor's version).

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