Final answer:
The observed angle of rotation in polarimetry is the degree to which an enantiomer rotates the plane of plane-polarized light. It is influenced by sample concentration, path length, light wavelength, and temperature. Polaroid sunglasses can be utilized to observe the effects of polarization and demonstrate the relationship between the angle of filter orientation and light intensity reduction.
Step-by-step explanation:
The observed angle of rotation in polarimetry refers to the measurement of how much an enantiomer's presence causes the plane of plane-polarized light to rotate. This measurement is crucial in the study of substances with chiral molecules that can rotate polarized light to the left or right; such substances are termed optically active. The angle of rotation is affected by various factors: the concentration of the optically active substance, the path length through which the light travels within the sample, and the wavelength of the polarized light, as well as temperature conditions during the experiment.
During polarization experiments, a significant angle between the direction of polarization and the filter axis is necessary to reduce the intensity of the light substantially. For example, at an angle of 45°, the light's intensity reduces to 50% of its original value, and at approximately 71.6°, it approaches zero intensity. This demonstrates the symmetric nature of polarized light intensity relative to the filter's orientation. Such insights can be explored with simple devices such as Polaroid sunglasses, which allows one to observe changes in light intensity when looking at reflective surfaces by rotating one lens relative to another.