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Week 10 Handout

Week 10 Handout - Week 10 Handout Lecture 21 Visual Signal...

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Week 10 Handout Lecture 21: Visual Signal Production and Transmission Production Methods: 1. Reflected Ex. Frigate birds (red chest) 2. Self generated Ex. Fireflies Temporal patterns and flight patterns differ between species Fireflies in Southeast Asian have patterns that function on a group level Fireflies in US function at an individual level Femme fatale- female firefly that is able to mimic the light signals of other species to attract males. She then eats the males. Properties of Light: 1. Intensity= Brightness= rate of photons hitting a unit surface (black and white phenomenon independent of color) 2. Hue= dominant frequency (frequency with the greatest intensity) 3. Chroma= saturation (purity) of the dominant frequency (when there is only a single frequency, then it is 100% pure). Light signals can be varied by: 1. Spatial characteristics (ex. Patterns) 2. Temporal variability (ex. Firefly signal) Ex. Squid, fish, lizards Use of melanin (fish), iridiphores and melanophores (fish) and chromatophores (squid) to change color at will. Cephalopods’ chromatophores each has its own neuron which allows for rapid information exchange through color changes (cuttlefish). Mechanisms of color production: 1. Pigments absorb certain colors, what isn’t absorbed is reflected back and is the color the object appears. 2. Thin layer interference can result in destructive (dark) and constructive (bright) zones. These types of interferences have two reflections (primary and secondary). The color changes based on the thickness of the thin layer. Ex. Butterflies that have translucent scales. The butterfly appears blue not because of pigment but because of thin layer interference. When oil is added to the butterflies wing (to increase the layer’s thickness) the color changes (this wouldn’t happen if it was rayleigh scattering producing the blue color).
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3. Rayleigh scattering produces the blue color in fish, lizards and birds. Particles of the right size are embedded in these animals surfaces to create scattering. Ex. Blue bird
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Week 10 Handout - Week 10 Handout Lecture 21 Visual Signal...

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