At the end of each semester, seniors present to the physics department the results of their Phys 489/490: SYE Advanced Laboratory and Phys 499: Honors SYE research projects. The abstracts for their research follow below:
Building a Low-cost Stokes Polarimeter - Blaine Ayotte '17
Polarized light has potential applications in fields such as forensics, food quality control, and cancer diagnosis. However, the instruments used to monitor the polarization of light (known as Stokes polarimeters) are expensive, and thus, not readily accessible to researchers and students in undergraduate settings. The goal of this project was to build an accurate Stokes polarimeter from cheap (~$100), non-ideal polarizers and waveplates making polarimetry research more available. We achieved accuracy for the circularly-polarized component of light (S3) within ±0.025. We also used our polarimeter to measure rotations in plane polarized light caused by optically active sugars (D-Fructose and D-Glucose). Using a red laser (633nm) we measured the specific rotation of D-Fructose with a percent difference of 3.7% and D-Glucose with a percent difference of 4.0%. With a green laser (543nm) we measured the specific rotation of D-Fructose with a percent difference of 7.3% and D-Glucose with a percent difference of 37.8%.
For more information, contact Dr. Munir Pirbhai
Characterizing the Magnetic and Temperature Dependence of Birefringence in the Liquid Crystal 4-cyano-4'-pentylbiphenyl (5CB) - Wenyao Zhang '17
Phase transitions are ubiquitous in nature. While most phase transitions are studied as temperature dependent functions, few target on other externally imposed constraints, such as magnetic field. Here, we examine both the magnetic induced and temperature induced birefringence in 4-cyano-4'-pentylbiphenyl (also known as 5CB), as two ways to observe and measure the phase transition in the liquid crystal (LC) system. The liquid crystal 5CB is chosen as our analyte because it is in liquid crystal phase at room temperature and its properties have been well reported in the literature. In this project, it has been shown that the induced birefringence is directly proportional to the square of the magnetic field applied and inversely proportional to the temperature. The best phenomenological constant a and the supercooling temperature T* calculated from our experimental data are 2.2 ± 0.3×105 Jm-3 °C-1 and 32.7 ± 0.5 °C, respectively.
For more information, contact Dr. Catherine Jahncke