Discusses human ability to perceive repeated sensory stimuli in the visual system, and explains that its frequency fc has a critical value, under normal conditions, about 40 Hz. (GA)

Describes an experiment in which students work together in small groups, take data, and make a calculation to roughly determine the diameter of the blind spot in their eye. (WRM)

Describes an experiment enabling students to apply concept of diffraction, determine limits of their color perception, learn how to measure wavelength with a simple apparatus, observe continuous and line spectra, and associate colors with corresponding wavelengths. The homemade diffraction-grating spectrometer used is easily constructed. (JN)

Provides background theory and an experiment relating to chemometrics. Describes the phenomenon where solutions are dichromatic or dichromic. Discusses the difficulty students have in describing such solutions that appear to be several different colors at the same time. (TW)