Updated: 9/19/2019

Return to the Chromaticity Diagram


Basic Challenges

  1. (x,y,I) Space Completeness: Demonstrate that you can vary the relative eye cone response values (x,y) and the intensity of the maximal pixel emitter (I) to produce any color that can be displayed on a W3C-compatible screen.
  2. The Color Brown: Demonstrate how various shades of brown are produced on the Chromaticity Diagram.
  3. The Color White: Demonstrate that the color white is produced at any pixel by setting equal emissions from the pixel's three emitters.
  4. Color Shades: Describe how to determine the Diagram region representing shades of light blue and demonstrate doing it.
  5. Diagram Non-linearity I: Demonstrate that at any point on the diagram that is on a line between two vertices, the contribution of the third-vertex emitter is zero.
  6. Diagram Non-linearity II: Demonstrate that, at the visual midpoint between two vertices, the contributions of the emitters at those two vertices are not equal.
  7. Unique RGB Components: Explain why, at any particular (x,y,I) position within the RGB boundary, there is a unique set of RGB contributions.
  8. No Photon Color can be a mixture: Use the Diagram to explain why no photon color can be a mixture of photon colors.
  9. All non-photon colors are mixtures: Use the Diagram to explain why every non-photon color must be a mixture of photon colors.
  10. No Photon Colors on the Screen: Use the Diagram to explain why no photon color can be shown on a W3C-compatible screen.
  11. Non-Unique Photon Components: Explain why there are an infinite number of different photon combinations (spectra) that will produce any given color inside the Chromaticity Diagram boundary made by the visible-photon locus and the straight line connecting the two limits of the locus.

Advanced Challenges

  1. If a spectroscope is available show that it can be used to see the mixture of photons which are being used to produce any particular light-beam color.
  2. Describe what can go wrong if illuminating light does not have a spectrum similar to that of daylight.
  3. Describe the journey of a photon from an emitter in the interior of the sun to an absorber in the interior of the eye.
  4. Describe what is known about the journey of a nerve signal from a photon-absorber pixel in the interior of the eye to a consciousness of the pixel color in the brain.
  5. Describe how the "color of an object" (the color of a light beam coming from an object) can be calculated from the spectrum of the light incident upon the object combined with the spectral reflectivity data for that object's surface.

© Project Physnet, 2019; Contact: Peter Signell, signell@msu.edu