Talk:Light

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Former good article nominee Light was a good articles nominee, but did not meet the good article criteria at the time. There are suggestions below for improving the article. Once these issues have been addressed, the article can be renominated. Editors may also seek a reassessment of the decision if they believe there was a mistake.
April 8, 2006 Good article nominee Not listed
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edit·history·watch·refresh Stock post message.svg To-do list for Light:

Restructure according to the guidelines proposed in Wikipedia:WikiProject Science, ie. with the following main sections:

  • Introduction : importance of light for life and humans; brief history of the understanding of light; sources of light (man-made or natural)
  • Light in practice: (avoid theory here)
    • Types of light: normal(incandscent, fluorescent) HID (football stadium lights) New eco-watt fluorescent lights and how they change they way colors look., laser; visible vs infrared
    • Properties of light: Spectral characteristics, brightness, color, frequency, coherence, modulation, speed of light
    • Light in the Universe: appearance of light after big bang, sources of light, ...
    • Light in everyday life: How different light effect humans (depression), everyday sources, human eye
    • Light in industry: sources, conversion from/to electricity; some applications of light (laser, ...); application of optics
    • Light in science: spectroscopy, astronomy, interferometry (If tht were important, than it should be in those sections)
  • Light in theory: introduce quantum electrodynamics, explain how the current theory explains light and its applications
  • History
    • Older theories of light
    • History of measurement of the speed of light
Priority 1 (top)


section on color[edit]

When the average person thinks of light, they also think of color. Color is not a physical property of electromagnetic radiation, but this layman's article could use a section about color. Jonathan Tweet (talk) 03:32, 17 November 2014 (UTC)

Since light is that part of the electromagnetic spectrum that can be perceived with the visual system, it might be a good idea to have a small section on that, with pointers to articles that explain things in more detail. Color can be analyzed into three components: hue, saturation and brightness. All other factors being equal, hue corresponds to the dominant wavelength of the light. Dominant wavelength is when you take the spectral curve of the light, slice it into thin slices, adjust each slice for the sensitivity of the eye at that wavelength, then find the midpoint of the area of the resulting curve. All other factors are usually not equal. Hue can be strongly affected by brightness (Bezold–Brücke shift, saturation (Abney effect), color environment (Metamerism) and a bunch of other stuff. All other factors being equal, perceived brightness is proportional to the square-root of the intensity (photon flux per unit area of the retina) for a point source, or the cube-root for a non-point source. Saturation has issues too.Zyxwv99 (talk) 15:30, 18 November 2014 (UTC)
I think some of that may be too much info about visual system phenomena, and not close enough to the topic of this article which is the concept of (visible) light in physics. I'm actually quite interested in color science and psychophysics (etc.), and we can certainly have some pointers to the relevant articles, but I don't think we should actually go into so much detail that's specific to the architecture of the human visual system. Colorspaces like RGB are still quite psychophysical but have a closer relationship to the physical spectrum than do the many abstract colorspaces (like HSL/HSV/Lab/etc.) whose relevance stems from the nature of human visual system processing (more specifically, trichromat humans, since there are a lot of dichromat men and possibly some tetrachromat women) rather than the nature of light. DavRosen (talk) 19:39, 18 November 2014 (UTC)
I offered this gloss but it was reverted: "Color has traditionally been considered a property of light, but it is now understood to be a product of the neural activity associated with the firing of nerve cells in the eye. Different organisms perceive colors differently, and some animals see light from a different range of wavelengths." The point I'm trying to make is that frequency is a property of light but color is not. The wavelength of light is a physics issue, but the color of light is a psychology issue. When I sense the weight of an apple, I'm sensing a physical quality of the apple. When I see that the apple is red, it's only red to the brains that see it that way. Jonathan Tweet (talk) 19:43, 18 November 2014 (UTC)
Sorry, I'm the one who undid it. I know what kind of point you were trying to make and I agree with it in principle, but we need to find a more meaningful way to say it. Simply taking the description down a level to physiology doesn't address in what way color differs from light. Just for example, while light can contain any combination of intensities (and polarization) at any of an infinite number of wavelengths along the spectrum, human vision starts by integrating that with respect to three specific response functions to reduce it to a particular three-number summary (roughly, RGB or XYZ) -- but we certainly couldn't say something like that so early in the lead. Maybe just that color and brightness arise from an interaction between the properties of light and the specific characteristics of our visual system -- or maybe that's not very meaningful either. DavRosen (talk) 20:45, 18 November 2014 (UTC)
Light is a psychophysical phenomenon, just like sound. Our article on electromagnetic radiation is about the physics aspects of light. Of course there is no reason why physics can't be discussed here as well, but neither physics nor engineering should not be the primary focus. If it happens to work out that way temporarily, that is only because these articles are written by people who have the time to write them. Since I am not currently contributing to this article I am not going to criticize too much. (I am currently working on fixing the article on peripheral vision. Along the way I stumbled onto an interesting fact: the greatest concentration of cones in the human eye is at the edge of the retina, especially on the superior-nasal side. That plus a huge cone streak extending horizontally from the fovea, past the optic nerve, then spreading out and bending up to meet to cone-rich crescent or ring at the ora seratta. Unfortunately nobody can figure out what those cones are for.) I have noticed that many of our light- and color-related articles are heavy on physics and engineering, almost as if they were written by people who work in digital image processing. That may explain the peculiar obsession with RGB and the profound distaste for HSL and related color models. The concepts of hue, saturation, and brightness are fundamental to the phychophysics of vision, not only in humans, but in any organism that can make any sort of wavelength distinctions. Dogs and cats, for example, which have only two types of cones, or mantis shrimp which have thousands. Unlike RGB, it is biologically a completely device-independent model. HSL and related models are something else entirely: even though they involve the concepts of hue, saturation, and brightness, they are technological artifacts relevant to digital image processing. I have nothing against digital-image-processing-related terminology such as RGB being mentioned in this article, so long as it's clearly identified as occupational jargon. Zyxwv99 (talk) 15:37, 20 November 2014 (UTC)
As it stands, the present article is about light as physical phenomenon: a type of electromagnetic radiation (others include X-ray, Gamma ray, Radio wave, Infrared, Microwave and Ultraviolet because each is a significant topic in itself beyond the broader Electromagnetic radiation article). The main mention of vision in the present article is to define the "visible" wavelengths, which hardly makes it an article covering the related perceptual/psychophysical/physiological phenonmena, which already have (and deserve) their own articles such as Visual perception and Visual system, and even Photometry and Color which are also defined with reference to human observers. (Perhaps the present article should refer to those for further information.) The editors of Sound, in contrast, decided to make that article about both the physical phenomenon and the perceptual phenomenon: it says so explicitly at the beginning of that article. Because WP is not a dictionary, it isn't necessary that the article called Light cover all meanings or topics described by this word. The present Light article is in Category:Light, which in turn is in Category:Optics, Category:Electromagnetic spectrum, Category:Electromagnetic radiation, Category:Waves, and Category:Electrodynamics, none of which are psychological or biological per se. If you really think there should be a blanket article beyond Visual perception and Visual system that connects these in some additional way to light (and hopefully you might contribute to its creation), it could be called (just for example) Light (vision) (and could be added to Light_(disambiguation)), but I don't think this topic should be fully merged into the present article which stands well on its own. DavRosen (talk) 19:57, 21 November 2014 (UTC)
OK, you convinced me. This article already has an appropriate mix of physics and psychophysics, with physics in the dominant position. That's apparently how the topic has evolved since the days of Isaac Newton. Zyxwv99 (talk) 19:22, 28 December 2014 (UTC)

Appearance of Light[edit]

The visual system in humans and animals is complex and the brain’s visual modeling algorithm is unknown. Yet more can be said about the system then the explanations currently used.

To begin with, the data (in the form of energy) has no appearance and will not be called “light” wave which incorrectly suggests an appearance of energy. Instead I will use the terms optical energy. The distinction is necessary to distinguish the physical objects in reality from the visible appearances created by the brain. It should also be clear that the photoreceptors in the eye convert optical energy into neural energy. Therefore the form of brain appearance cannot be optical energy.

An individual optical shaft (“light beam”) contains tiny bits of data. In fact they are so tiny that the eye cannot detect them directly. Instead the eye (via the lens) converges many optical shafts on individual points called photoreceptors. The point of convergence becomes fixed by the photoreceptors. If they were not fixed, they would begin to diverge. So they are fixed. The photoreceptors also convert the optical energy to neural energy (they are transducers).

There are 126 million photoreceptors each at or near points of conversion. Those, that are at points of conversion, are perfectly merged (optically). Those, that are only near points of conversion are slightly diffuse (optically). In the brain’s appearances, the merged data is in focus and the less merged data are slightly out of focus. This suggests that the brain does not have the ability to focus slightly diffused data. What this means is unclear but it could be important to understanding the brain’s appearance function. Cognition does not relate directly to 126 million bits of data. If it did, the data would be extremely scattered, confusing and overwhelming. Seeing 126 million bits of data as a one, single assemblage is apparently impossible. Instead the brain merges the data and changes its form from neurological impulses to a single meaningful image.

Getting back to the photoreceptors, each one detects changing data as a person moves his head or eyes. Thus the data at each photoreceptor is constantly in flux and can change very rapidly. The sweep rate of photoreceptors must be extremely fast, perhaps in milliseconds. The ability of the photoreceptors to change, leads to the perception of movement.

Photoreceptors are not pixels. Pixels emit optical energy from a digital screen. Photoreceptors emit neurological data. The receptors of neurological data are in neurites. A number of neurites connect their parent neuron to a number of photoreceptors. This means that a group of bits from a set of photoreceptors are in the neuron at the same time. Alternatively, the neuron operates on the group of bits to form a “word” which is an internal, conceptual representation of the group. Perhaps the word is in a different neural language and that language condenses the bits into a correspondingly small signal with the new signal containing the connotation of the group but smaller than the combined size of the former signals. In other words the information (126 million bits) as it travels to the visual cortex in the brain, is transformed into ever consolidating forms (much like a written explanation can be consolidation into a diagram). The consolidations end with one overall appearance which has a meaning in total or in parts depending on a person’s attention. In other words, the final appearance model has extensive meaning in one image. The appearance model allows a person’s cognitive ability to pay attention to the appearance of individual objects but still be aware of what is going on elsewhere. An appearance is a whole with its own connotation and each of its parts have a connotation as well. This is not as overwhelming as 126 million individual photoreceptors which have 126 million separate nano-meanings. While I cannot fathom the steps in the consolidation function, I am enormously impressed by the final results of the appearance model.

The most difficult concept for me in developing my ideas in this letter was realizing that light does not have an appearance in physical reality. I now know that physical reality has material objects and energy but no appearances. Light is unknowable before the brain’s model of appearances. Some people have told me that a television creates appearances but a television does not. It creates optical energy in a form that the brain’s optical system uses to create visual appearances. The people designing televisions think they are creating appearances on the television sets but unbeknownst to them they are creating optical energy that will become brain appearances. They equate their brain’s created appearances with television’s optical energy. There is a correlation between the two but correlation doesn’t mean causation.

It should be noted that brain created appearances are unambiguous, consistent and reliable. On the other hand, words can be subjective, unclear, imprecise and ambiguous. When I use the word “model” I might be using the word in the computational sense (a form of computer program) or the more traditional sense of “representation”. I mean representation. But the word representation has a complex meaning in the theory of the mind which confuses the meaning of cognition with what is perceived. I mean “what is perceived”. Furthermore, the word “light” has different meanings that some people use interchangeably: the source of light, light energy, the sensation of light or the appearance of light. I mean “the appearance of light”.

And just to be absolutely clear, although it must be obvious, this paper is about one particular model, appearance, as opposed to taste, smell, sound, proprioception, pain and touch which are other models created by the brain.

I am not a dualist or, if given that epithet, I will insist that I have updated dualism to fit with modern science. But I did not conceive of a perspective and attempt to force the science. Rather I began with science and, with some insight, arrived at conclusions. My conclusions are meant to be coherent in whole and in part. In addition, if there were intangible, unexplainable images in reality that somehow appeared in the brain, that would be dualism. But there are actually shafts of optical energy in reality that do not appear in the brain because they are converted to brain images. That is not dualism. That is a descriptive explanation of the brain’s appearance model.

At any rate, I do not think that the silent, dark reality is the same as a visual form. To me appearance in reality is an unscientific perspective. There are no intangible, unexplainable appearances (mirages?) in reality. There are physical optical shafts. On the other hand, the brain’s form of appearances cannot be intangible but must be built out of brain matter perhaps in the form of subatomic particles. I do not know how the matter is arranged or formed but I deduce that an unknown form exists and that there is an unknown form for the connection to cognition as well. The form is certainly material and not in the form of an intangible mirage. If the mirage in reality exists, it cannot be a brain substance. It must be something metaphysical and unknowable. Physical reality has no appearances (mirages). If it did, then the brain’s optical system would not be necessary. Cognition would connect directly to reality’s “mirages”. But the form of the brain’s appearances must be a transformation of energy into a form required by cognition. In other words, cognition must call for a specific form which drove the evolution of the brain’s optic system. The eyes, neurons and processes in the optic system support cognition. They don’t support themselves. If a simpler human form was possible, the brain’s components would be smaller.

This letter uses appearances as an example but a similar thinking applies to all the other senses. — Preceding unsigned comment added by Jayjacobus (talkcontribs) 17:16, 28 January 2015 (UTC)

Possible external link[edit]

Cartoon video showing experiment in which light is seen as both a particle and a wave here. If worthy, for people who follow this page and know about the science of light, consider adding it as an external link.--Tomwsulcer (talk) 13:56, 3 March 2015 (UTC)

Attempt to explain Diffraction by using particle nature[edit]

By Einstein's energy mass equality,if we consider light to be consisting of particles as suggested by quantum theory, a light quanta will be possessing negligible mass. On contact with other particles it may experience an attractive force like the nuclear force which is effective in short range. This force may be capable of providing a centripetal force to the quanta thus changing its course before it goes out of range.The great velocity and the negligible mass ensure that the effect of the force exerted by the diffracted quanta is negligible as the momentum of the quanta is also negligible and it goes out of range before causing any observable effect like getting absorbed.If you obstruct the path of a fine jet of water with a cardboard you will observe that the direction of the water particles near the cardboard is altered.The path is similar to the one followed by light on being diffracted.If the single slit diffraction experiment for light is repeated with water or ink the results obtained also match the ones obtained by using light sources as the path is similar to the one followed by light provided the speed of water remains constant. Shreyas Keelary (talk) 15:28, 4 March 2015 (UTC)Shreyas Keelary

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                                                                          firma:ghq8oysdiug  — Preceding unsigned comment added by 177.225.212.126 (talk) 23:42, 17 March 2015 (UTC)