the nature and composition of light sources to which the human eye responds?
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It is the range of frequencies from about .7-.4 micrometres.\nWhite light is not a frequency it is the combination of all frequencies in the visible spectrum. The cones in our retina are sensitive to these frequency differences while the rods are sensitive only to the intensity (black & white). The pupil does not respond to light outside of the visible frequencies, therefore infrared and ultraviolet light can easily damage our retinas.
202376
The most important - light sensitivity.
353617
Optical Spectrum Analyzer (OSA) is probably what you're looking for...nice for discovering chemical composition of light source and probably a zillion other different things.
1160277
Theoretically, the answer is no; all people do not see the same shade and intensity of color.  Color vision occurs as a result of specialized photo-receptors in our eye.  The number of these receptors can differ from person to person, and as a result, some people may be more sensitive to certain colors than others.  A simple way to test this would be to take freshly isolated retinas from various individuals (ie: laboratory animals) such that the photoreceptors (rods and cones) are still intact and expose the retinas to lights of different wavelengths (ie: colors) and intensities while simultaneously recording the neuronal output generated in response to the lights.  I haven't done such an experiment myself, but it is very logical to assume that no two individuals would respond the same way to the lights, since perception of the light stimulus depends on the frequency and duration of the activation of the receptor neuron as well as the number of receptor neurons activated and their distribution in the retina.
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1)Sunlight\n2)Twilight\n3)Midnight\n\nno joke, this is true. See link below.
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Sorry, wagonpaws is not correct. A 6000K blackbody (like the Sun) has a peak output at .483 microns (483 nm), which is blue. But .55 microns (550 nm) is the wavelength that human eyes are most sensitive to.
1131053
the retina is the sensory layer of the eye, and it contains two types of sensory cells: rods and cones.  rods are great for seeing in dim light and detecting motion and shapes.  cones require brighter light and enable us to see colors and detail.  you can see a good diagram here: http://www.usm.maine.edu/psy/broida/101/retina.JPG\n\nthe retina is not a uniform mixture of rods and cones.  cones are concentrated at the fovea, which is a thinner layer of cells (in fact it is entirely cones, no messenger cells or anything else).  the light reflecting off objects in the center of your visual field is received at the fovea.  the rest of the retina contains mostly rods, with a few cones mixed in.  since the rods are more at the sides of your retina, and they are better at detecting light (even very dim points of light) and motion... when you are in the dark you tend to have really good peripheral vision.  look at the night sky on a clear evening.  concentrate on seeing the stars directly in front of you.  do any of them look not particularly bright?  now turn your head and try to see those dim stars through your peripheral vision.  they look much brighter, don't they?\n\nit takes a few moments for the eye to switch between primarily cone-vision and primarily rod-vision.  you can test this by going from a well-lit area to a dark area, such as enterring a movie theater from outside (daytime).  when you are outside, your eyes are adjusted for cone vision and you see lots of colors.  when you go into the theater, you can't see anything for a minute or so, then your eyes slowly adjust and the rods take over.  it gradually gets better... you can see shapes and recognize friends across the room, but everything is in shades of bluish gray.  if you then leave suddenly and enter a bright room or go outside, your eyes switch back to cone vision after a bit.\n\nthere is another thing i haven't mentioned: the pupils.  these are holes in the eye surrounded by smooth muscle.  the muscles control the size of the opening.  cameras work in a similar fashion... if too much light is coming in, things get "overexposed", it is hard to make out any detail.  you are effectively blind, until your eyes adjust.  it can be painful, too, if the amounts of light are significantly different.  you will probably notice this if you decide to fix your bulbs and continue to make nighttime trips to the bathroom.  when there is not much light, the pupil opening widens.  the maximum opening of the pupil is about ten times the size of the minimum opening.\n\nentering your dim bathroom from full sun is like going into the dark theater.  if you stay there long enough, your rods will kick in and you'll see just fine.  entering your dim (but lit) bathroom from complete darkness is like leaving the dark theater.  your cones take over.  in either case, you don't see "better" than usual, your eyes just adjust so that you are at your normal ability.
730478
White light is a combination of many wavelengths of the visible light spectrum.  As these wavelengths pass through water droplets suspended in the air, they are refracted at different angles.  Because of the angle of refraction, and because each wavelength of light is bent at a different, specific angle, the result is the division or sorting of light into wavelengths, which the human eye then perceives as color.\n\n:) Hope this helps!
1139150
A good question. We perceive color because each of the cones in our eyes is receptive to only a specific range of frequencies, and so light of a given frequency will only stimulate some of these cells and not others. Any combination of light that stimulates the same cells by the same amount will be perceived as the same, even if spectroscopically it is quite different. Yellow light, such as that emitted by sodium vapor, falls well within the frequency range of both the "red" cones and the "green" cones, and so stimulates both, causing us to perceive yellow. However, if we were to provide both red and green light simultaneously, the red cones would be stimulated by red light and the green cones by green light, and we would also perceive yellow. Because we have but three types of cones, we can, both in principle and in practice, provide the perception of (almost) any color of light by varying luminosities of just the three primary colors, which is why we say that other colors are combinations of these three primary colors. However, monochromatic light of a frequency in between the frequencies of the primary colors will also appear to be a secondary color, even though it is obviously not a mixture of primary colors. Thus the grade school simplification of other colors as being literally composed of the three primary colors is, I'm afraid, quite misleading.
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Radio Waves\nInfrared light\nVisible Light\nGamma Rays
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The sky appears blue to us on a clear day, because the atoms of nitrogen and oxygen in the atmosphere separate the suns white light into its many colours, and scatter them throughout the atmosphere.The wavelength of the blue light scatters better than the rest, predominates over the other colours in the light spectrum, and makes the sky appear blue to us.The scientific name for this phenomenon is the Tyndall effect, more commonly known as Rayleigh scattering.\n\nThis phenomenon describes the way in which light physically scatters when it passes through particles in the earths atmosphere that are 1/10th in diameter of the color of the light. The light spectrum ranges in wavelength from red to violet, and, since the wavelength of the blue light passes through the particles with greater ease than the wavelengths of the other colors of light, the sky appear blue to the naked eye.\n\nThe human eye has three types of light receptors, known as cones, located in the retina. The cones are either considered to be red, or blue, or green, based upon their strong response to light at these wavelengths. As light stimulates these receptors, our vision translates the signals into the colors we see.\n\nWhen gazing at the sky, the red cones respond to the small amounts of red light scattered, and even less strongly to the orange and yellow wavelengths. Although green cones respond to yellow, their response to scattered green and green-blue wavelengths is stronger. Finally, colors near the strongly scattered blue wavelengths stimulate the blue receptors.\n\nIn short, the skylight stimulates the red and green cones almost equally, while stimulating the blue cones more strongly. For these reasons, our vision naturally adjusts as clearly as possible to separate colors.
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In an eye, there are photo-receptors made out of cells which are shape like cones and rods... \n\nWhen a cat, for example, is in a dark room, its pupils dilate wide and the minimal light in the room reflects inside the cat's retina where the photoreceptor's absorbs and creates this luminescence...
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http://en.wikipedia.org/wiki/Eyesight
43367
Each of the eyes are slightly recessed, and each eye points in a slightly different direction.  This makes it so that depending on which eye detects the most light, the insect is able to determine the direction of the light.  Humans, by contrast, find the location of light by having a lens which focuses the incoming light on the photo-sensitive retina at the back of the eye.
1184007
The colored part of your eye is the iris, and all it does is control the amount of light that passes into the eye by varying the size of your pupil.  Light passes through that opening to the retina at the back of the eye where the rods and cones convert the lightwaves into the nerve signals that your brain recognizes as objects, colors, etc.
17833
To elaborate on the previous response: Color is merely your brain's interpretation of light (electromagnetic radiation in the visible spectrum) entering your eye. A difference in color corresponds to a difference in the light's wavelength. And just as there are an infinity of numbers between 0 and 1 (fractions), you could also technically say there are an infinite number of colors between the shortest wavelength of visible light and the longest. This is the answer you'd get from a physicist.\n\nBut, a physiologist/neurologist might have a different answer. As I stated, color is an interpretation of the chemical reaction between light and the rods and cones in the back of your eye. The fact that it's an interpretation and the fact that we can't detect very small differences in wavelength suggests that there is a much smaller set of colors that we, as humans, could define given our very limited built-in equipment (our eyes). Even among humans it varies though, I have no idea what my girlfriend is talking about sometimes. It's not for lack of trying, my eyes/brain (as with many guys) is capable of detecting a smaller set of colors than girls. Is her set more valid than mine?\n \nAnd I'm sure an artist and a poet would tell you something completely different :)
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The eye it not limited by distance;\n\nit responds to photons hitting the retina, it does not care how far the photons have travelled.\neg you can see a bright star further away than a dim one because it emits more photons. A telescope serves to collect more photons.\nIn a dark room you cannot see even close objects.