On Day 20, we covered two different topics.

We first discussed how reflection and refraction affect the saturation of pigments.

Reflection and Refraction in pigments from Seeing the Light: Optics in Nature, Photography, Color, Vision, and Holography by David R. Falk, Dieter R. Brill , David G. Stork. Wiley, 1986.

We then moved on to some basic quantum mechanics in order to explain why various pigments absorb and reflect different wavelengths. We used a simple model of atom energy levels of sodium. New concepts introduced included

• Photons and their energy E=hc/λ
• Quantized atomic energy levels
• Energy levels of sodium
• Emission and absorption spectra of gases

Sources: Nassau, Kurt “The Causes of Color,” Scientific American, October 1980, pages 124-154.