Chapter 15: Light, color and atmospheric optics

1. Chapter 15: Light, color and atmospheric optics • White and colors • White clouds and scattered light • Blue skies and hazy days • Red suns and blue moons • Twinkling, twilight, and the green flash • The mirage: seeing is not believing • Halos, sundogs, and sun pillars • Rainbows • Coronas and cloud iridescence

2. White and colors

3. White and colors • review of fate of visible light passing through the atmosphere • review of relationship between wavelength and colors

4. White clouds and scattered light

5. White clouds and scattered light • reflection • scattering • Thunderstorms appear dark because the clouds(cumulonimbus) are about 10 km deep, scatteringmost of the light.

6. Blue skies and hazy days

7. Blue skies and hazy days • selective scattering • effect of scattering particle size • crepuscular rays

8. Red suns and blue moons

9. Red suns and blue moons • path length of sunlight passing through the atmosphere • atmospheric particle effects • The “definition” of a blue moon as two full moons ina single calendar month has nothing to do with atmospheric optics.

10. The mirage: seeing is not believing

11. The mirage: seeing is not believing • inferior mirage • superior mirage • Mirages are very common and may be seen frequentlyif you look for them.

12. Inferior mirage • warm surface, decreasing temperatures aloft • The proper conditions for an inferior mirage are commonlyfound over a hot road surface during summer, or overan unfrozen lake on a very cold day.

13. Superior mirage • cold surface, warmer temperature aloft • The proper conditions for a superior mirage are commonlyfound over water and over snow-covered surfaces.

14. Fata morgana • complex vertical temperature profile • According to legend, King Arthur’s half-sister, Fata Morgana in Italian, was a fairy enchantress trained by Merlin the Magician. She lived in a crystal palace beneath the water and could build fantastic castles from thin air.

15. Halos, sundogs, and sun pillars

16. Halos • ice crystals • dispersion • Halo-producing ice crystals are commonly found in cirrostratus clouds

17. Sundogs • hexagonal ice crystals • horizontal orientation • Sundogs are commonly seen when cirrostratus cloudsare in the sky.

18. Sun pillars • reflection phenomenon • Sun pillars can be seen shortly after sunrise orshortly before sunset on very cold days.

19. Rainbows

20. Rainbows • water droplet phenomenon • reflection and dispersion • necessary conditions for a rainbow • the primary rainbow

21. The secondary rainbow • two internal reflections • A tertiary rainbow also exists, but it is too faint tobe seen with the human eye.

22. Coronas and cloud iridescence

23. Coronas and cloud iridescence • diffraction

24. The corona • necessary conditions

25. Cloud iridescence • another water droplet diffraction phenomenon

26. The Glory • necessary conditions for viewing • It is very common to see a glory from the windowof an airplane. Make sure you are sitting on theside opposite the sun.