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Color and Spectral Signatures. Steve Dutch University of Wisconsin-Green Bay. It’s a Colorful World. Color and Wavelength. Color Formalisms. Physical Optics Scattering is most important in Remote Sensing Color Centers and Crystal-Field Effects Individual atoms interact with light
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Color and Spectral Signatures Steve Dutch University of Wisconsin-Green Bay
Color Formalisms • Physical Optics • Scattering is most important in Remote Sensing • Color Centers and Crystal-Field Effects • Individual atoms interact with light • Inter-Atomic Interactions • Charge transfer • Molecular orbitals • Vibrations • Band Theory • Applicable to radar, not much to passive remote sensing
Physical Optics • Scattering • Particulate Matter • Dispersion • Rainbows, etc. • Interference • Oil slicks, sea shells • Diffraction • Opal, CD’s
Major Types of Scattering • Rayleigh scattering • Small particle compared to wavelength of light • Mie scattering • Particle about the same size as wavelength of light • Geometric scattering • Particle much larger than wavelength of light
Rayleigh Scattering • Molecules and nanoparticles • Proportional to 1/λ4 • Blue vs. Red = (700nm/400nm)4 = 9.4 • Why the sky is blue • Why isn’t the sky purple? • Less sunlight • Lower eye sensitivity • Greater absorption • UV Scattering useful in particle studies
Mie Scattering • Responsible for most white colors • Cloud particles • Oil droplets in contaminated water • Suspended sediment • Algal blooms
Fluorescence(Sunlight and laser induced fluoresence in chlorophyll)
Charge Transfer • Electron bumped between atoms • Extremely effective absorption mechanism • A major reason UV is not very useful for surface remote sensing • Very strong UV and blue absorption in iron oxide • Why we have “earth tones”
