Henry M. Gunn High School

Optical Rotation: First Attempt

Experimental Description/Abstract:

DIAGRAM

We determine the effect of sugar solution on the polarization of fixed wavelength laser light. In an experimental set-up with no sugar solution, the vertical and horizontal polarizers will extinguish the laser light before it reaches the OPM. However, by adding the sugar solution, this vertically polarized light is tilted such that the horizontal filter does not extinguish the light. By adjusting the direction of the horizontal filter through a rotatable mount, we can find the angle at which the filter extinguishes the light. In addition, tests are conducted on each piece of equipment which helps optimize the experiment. The purpose of this experiment is to collect data about the performance of different equipment pieces and see which adjustments to this equipment yield the desired results.

 

Materials:

Procedure:

  • Prepare sugar solutions with the three types of store-bought sugar by mixing 45g of sugar in 50ml of distilled water. Stir until sugar is dissolved. In total, four vials, one vial for each sugar and one vial of distilled water (for control), should be prepared.
  • Setup mounts - Screw five mounts equidistant from each other, horizontally placed on the pegboard, from left to right for equipment such that each piece of equipment is held by a mount (see diagram). The mount placed at position four should be rotatable.
  • Equipment Optimization and Operation Correction - Consists of three separate tests of the equipment,
    (a) Laser to Detector,
    (b) Accuracy of Polarizer/OPM,
    (c) Accuracy of the Rotatable Mount.
    • Laser to Detector - yet to be decided upon with Dr. Alloway
    • Accuracy of Polarizer/OPM - Place the first polarizer on the position two mount and the second polarizer on the position four rotatable mount at an angle orthogonal to the first polarizer. Calibrate the rotatable mount to 0 degrees in this position. Mount the laser pointer at position one and the OPM at position 5. Fire the laser through the apparatus and observe the amount of photons detected. Adjust the angle of rotation on the fourth mount such that a lesser amount of photons are detected. Based on this test, find the lowest amount of photons detected possible. Record the angle rotated and corresponding amount of photons detected.
    • Accuracy of the Rotatable Mount - Using the angle measured in step (b) and with the same resulting set-up, rotate the mount 90 degrees from its current position. Record the number of photons detected. Slightly tilt the mount left and right and record if the number of photons increases. Repeat steps (b)-(c) with each team lab member.
  • Setup equipment - refer to numerical labels in diagram for where to place equipment. The fourth piece of equipment (horizontal polarizer) should be placed at zero degrees and orthogonal to the vertical polarizer which is found at position two.
  • Reduce noise/Isolate other variables - Prepare the cardboard isolation system: staple black velvet cloth to the inside lining of the cardboard box. Make sure all holes are covered. Close all blinds on windows, shut off A/C or heating system and dim the overhead lights.
  • Control - Fire laser through the vial of distilled water and adjust the angle of the horizontal polarizer such that no photons are detected on the OPM.
  • If control trial is successful, replace the vial of water with one of the vials of sugar solution. Turn on the laser and zero out the horizontal polarizer such that no photons are detected on the OPM. Record the angle of rotation. Repeat steps 5-6 ten times for each type of sugar solution.