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The Purple Earth Hypothesis (PEH) is an astrobiological hypothesis, first proposed by molecular biologist Shiladitya DasSarma in 2007, [1] that the earliest photosynthetic life forms of Early Earth were based on the simpler molecule retinal rather than the more complex porphyrin-based chlorophyll, making the surface biosphere appear purplish ...
Purple haze refers to a state of mind induced by psychedelic drugs, particularly LSD. [86] Wearing purple is a military slang expression in the U.S., Canada and the U.K. for an officer who is serving in a joint assignment with another service, such as an Army officer on assignment to the Navy. The officer is symbolically putting aside his or ...
If photons of a particular wavelength are absorbed by matter, then when we observe light reflected from or transmitted through that matter, what we see is the complementary color, made up of the other visible wavelengths remaining.
Photons seem well-suited to be elements of an extremely fast quantum computer, and the quantum entanglement of photons is a focus of research. Nonlinear optical processes are another active research area, with topics such as two-photon absorption , self-phase modulation , modulational instability and optical parametric oscillators .
Purple bacteria or purple photosynthetic bacteria are Gram-negative proteobacteria that are phototrophic, capable of producing their own food via photosynthesis. [1] They are pigmented with bacteriochlorophyll a or b , together with various carotenoids , which give them colours ranging between purple, red, brown, and orange.
In the 18th century, purple was a color worn by royalty, aristocrats and other wealthy people. Good-quality purple fabric was too expensive for ordinary people. The first cobalt violet, the intensely red-violet cobalt arsenate, was highly toxic. Although it persisted in some paint lines into the 20th century, it was displaced by less toxic ...
This return to stability corresponds with the release of excess energy in the form of fluorescent light. This emission of light is only observable whilst the excitation light is still providing photons to the fluorescent molecule and is typically excited by blue or green light and emits purple, yellow, orange, green, cyan, or red.
Blue, direct diode semiconductor lasers can be built using inorganic gallium nitride (GaN) or InGaN gain medium, upon which many (dozens or more) layers of atoms are placed to form the active part of the laser that generates photons from quantum wells. Infrared lasers built on gallium arsenide (Ga As) semiconductors use similar manufacturing ...