Q: What is the origin of a rainbow?
Q: Consider the curve that describes the minimal wavelength difference that is required to discriminate a pair of spectrally pure lights as a function of their wavelengths. For trichromatic humans, this curve has a distinctive and complex shape, with minima at about 480 nm and 580 nm. How can we explain this distinctive shape?
Q: Starting with a pair of M and L pigment genes in their normal head to tail tandem arrangement, with the L pigment gene 5’ of the M pigment gene, draw the various products that arise from homologous intergenic and intragenic meiotic recombination and predict the color vision phenotypes that would be conferred on a male who inherited each of the resulting X-chromosomes. Note that the hybrid pigments that are produced from M/L or L/M hybrid genes (following intragenic recombination) invariably have absorbance spectra that are in the interval between the normal M and L pigments. As a more advanced exercise, try starting with X-chromosomes each of which carries one L pigment gene followed by two M pigment genes (the most common arrangement in the human gene pool).
Q: Thus far, there are no reports of anomalous trichromats with a visual pigment that has a spectral sensitivity at longer wavelengths than the normal human L pigment. Is this surprising?
Q: For humans, the visible region of the spectrum ranges from about 400 nm to about 700 nm. Is vision possible beyond this range?