Optical activity: an improved demonstration

Abstract

This demonstration on optical activity adds to a previously described demonstration making it more impressive and instructive.

Kaleidoscoptical Activity

“…It should be emphasized, that similar to the situation in the real atmosphere, the observed temperature effects are caused not only by radiation processes, but also are due to thermal convection and heat flow. One can show, however, by measuring the temperature simultaneously with a thermocouple in the beakers and an infrared-sensitive probe from above, that in our experiment radiation contributes to a considerable extent to the measured temperature polarized light by an optically active substance (1)(2)(3)(4)(5). The common set-up is shown in Figure 1.…”

Low-Cost 3D-Printed Polarimeter

“…Typically, the optical activity of substances is only demonstrated by the teacher/instructor − at the high school level and during introductory chemistry college courses. The demonstration usually involves overhead projection technology. − There is an example of a zero-cost polarimeter that is based on a mobile phone and sunglasses.…”

Is That a Polarimeter in Your Pocket? A Zero-Cost, Technology-Enabled Demonstration of Optical Rotation

“…Practical demonstrations, conducted by a lecturer in front of an audience, are as old as science teaching itself . Demonstrations involving the transmission of light, for example, solution-state color changes in chemistry, have been conveniently presented to large audiences using overhead projection technology for many decades. , One area that this has been applied to with great success is that of optical rotation: the phenomenon of the rotation of plane polarized light by molecules that exhibit chirality. − Such demonstrations can be readily converted into hands-on experiments, − but the requirement for specialized or self-constructed equipment presents a barrier to entry.…”

“…Literature values for specific rotation are cited at a particular temperature and monochromatic wavelength, most commonly 589 nm. Specific rotation is different at different wavelengths, so for this reason, measurements taken in the lecture theater using white light sources also exhibit optical rotatory dispersion (colored fringes of light on either side of the angle of minimum transmission) . Demonstrations, then, are usually limited to qualitative observations, such as the equal and opposite optical rotation of enantiomers, or the modification of chiral activity during a solution-phase reaction. , …”

“…Specific rotation is different at different wavelengths, so for this reason, measurements taken in the lecture theater using white light sources also exhibit optical rotatory dispersion (colored fringes of light on either side of the angle of minimum transmission). 5 Demonstrations, then, are usually limited to qualitative observations, such as the equal and opposite optical rotation of enantiomers, or the modification of chiral activity during a solution-phase reaction. 7,22 Demonstrations also require the use of polarizing film, and equipment to hold and rotate this film.…”