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Corvids (and raptors) are reported to not see UV Håstad et. al. 2005. However, American crows are reported to recognize sex-specific differences in plumage that are invisible to humans Eaton 2006. Unfortunately, I don't have access the latter paper so I don't know what the basis for that discrimination is or how to reconcile that result with those of ...


3

this is a chart of the light activation of the light sensitive cells in the human eye. see that little blip up on the tail end of the red cone, that minor ranges means the extreme blue end of the spectrum activates blue cones but also has a chance to activate red cones. That is why you can sometimes see magenta tinges in bluest of blue light. There is also ...


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A recent study published in Nature by Tinsley et al. Direct detection of a single photon by humans found that it is possible for dark-adapted humans to respond to a single-photon stimulus, but only rarely. They used a source which created pairs of photons, and used one of the pair to determine whether the subject may have been exposed to a single photon. The ...


8

Technically, we can sense the individual photons. Here is an quote from a cellular biology textbook: "Absorption of a single photon of light induces a conformational change in the rhodopsin molecule, which transmits a signal to a heterotrimeric G protein (called transducin ), which activates a coupled effector." (Karp's Cell and Molecular Biology 8e, 603). ...


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A single molecule of rhodopsin (actually the cis-retinal bound to it) can and actually does react to one photon (Purves et al. Chapter: Phototransduction in Neuroscience). It has been estimated that a single light-activated rhodopsin molecule can activate 800 transducin molecules, roughly eight percent of the molecules on the disk surface. Although ...


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