What is Eye: Definition and 268 Discussions

Eyes are organs of the visual system. They provide animals with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and convert it into electro-chemical impulses in neurons. In higher organisms, the eye is a complex optical system which collects light from the surrounding environment, regulates its intensity through a diaphragm, focuses it through an adjustable assembly of lenses to form an image, converts this image into a set of electrical signals, and transmits these signals to the brain through complex neural pathways that connect the eye via the optic nerve to the visual cortex and other areas of the brain. Eyes with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system. Image-resolving eyes are present in molluscs, chordates and arthropods.The most simple eyes, pit eyes, are eye-spots which may be set into a pit to reduce the angles of light that enters and affects the eye-spot, to allow the organism to deduce the angle of incoming light. From more complex eyes, retinal photosensitive ganglion cells send signals along the retinohypothalamic tract to the suprachiasmatic nuclei to effect circadian adjustment and to the pretectal area to control the pupillary light reflex.

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  1. P

    How Much Power Should an LED Emit to Be Visible from 5 Meters?

    Homework Statement In ideal conditions human eye can feel something if 100 photons with wavelengh of 5500A fall directly tu human eye in one seconds time.LED(lambda=5500A) is placed 5m away from human eye. Homework Equations Calculate the power of LED to achieve that the human eye can...
  2. J

    Can the human eye detect just a single photon?

    First off, is a photon just one wave cycle of an EM sine wave (2∏). If so, could the human eye detect just a single photon by itself?
  3. B

    Optics/ the eye/ near, far-sightedness

    Hello all, I'm having trouble understanding the human eye and what the focal length has to do with where light converges. Why do we need a longer focal length to see distant objects and shorter to see near objects? Thank you
  4. C

    Resolution of points by human eye

    I'm trying to teach myself optics from Frances Sears' book Optics from 1949. I'm attempting every problem, and there are answers to the odd ones in the back. I've gotten a lot of wrong answers and don't know why, had a few I just couldn't even see how to start, and at this point, I'm seeing...
  5. S

    How can squinting be used by both a myopic & hyperopic eye?

    I am a myope, and I can squint to focus what normally would be a distance that is beyond my range of focusing. I figure that this is due to the eyeball being deformed, making the profiles of the cornea & lens be less pronounced - or perhaps by shortening the eyeball (which would seem to be the...
  6. D

    Can the Venus transit be viewed with the naked eye

    Can the Venus transit be viewed with the naked eye? I do have a solar filter (from the anstronomy department of a university), so this isn't about safety issues. The question is would I need a telescope to oberve the dot or can I just look at it?
  7. F

    Eye diagram telecommunications

    Homework Statement draw the eye diagram you would expect to see should a digital signal be passed through a transmission line with a bandwidth limited to three times the maximum bit rate of the digital signal. the answer is "Only f1 and f3 pass through" My question is, what about f2 ? Why...
  8. F

    Naked eye view from intergalactic space

    If one were located in intergalactic space, say halfway between the Milky Way and Andromeda, what would space look like to the naked eye? Would we see a relatively small number of galaxies and otherwise mostly just darkness? From that position would the Milky Way and Andromeda have any...
  9. E

    How quickly does a star's supernova become apparent to the naked eye?

    If a star in our night sky were to go supernova, how quickly does this become apparent to the naked eye? I know the star collapses very quickly, but what will this look like to the naked eye? Will the star suddenly become brighter within seconds or minutes, or gradually over hours or days?
  10. M

    Predicting eye color genotype?

    I have a question. My parents have green eyes, one sister has brown eyes, another has hazel eyes and the last sister & I have blue eyes. Given this information, how can I determine what eye color alleles I might pass on to my children? No, I'm not trying to predict my childrens' eye color...
  11. K

    Understanding Lens Flare: Causes and Observations | Light Phenomenon Explained

    Hey I've been looking around about lens flare's within the eye. well not necessarily lens flares, but the category it falls under and what exactly is it. Just wondering if anyone here know's where I can find it or tell me what exactly it is and causes it. Basically when I look at street...
  12. M

    Medical White reflections in photos in one eye

    Is this something to be worried about? I know it can be a sign of cancer in children but its very uncommon even above the age of 1. I have always had bad vision in the white-reflecting eye (I think this might be amblyopia?). After searching around the internet I found a few other people with the...
  13. W

    Rayleigh Criterion related to the eye

    I am doing a Mastering Physics problem that I am stumped on. The question is: "If this resolving power is diffraction-limited, to what effective diameter of your eye's optical system does this correspond? Use Rayleigh's criterion and assume that the wavelength of the light is 550 nm ." The...
  14. E

    Could I Have Damaged My Eye With a Laser Level?

    Could be over reacting here but since I know nothing of lasers: I lased my eye accidently with a laser level, http://www.homedepot.com/buy/tools-hardware/hand-tools/strait-line/laser-level-114624.html, it is a CLASS 111A labled with a DANGER label. I stuck it to wall and when I pulled it off...
  15. K

    A fun trick to see the vasculature of your eye

    In this video, the narrator explains why you aren't normally able to see the network of blood vessels in front of your eye, and a neat trick to actually see it. I thought it was really cool. http://www.youtube.com/watch?v=L_W-IXqoxHA&t=3m8s
  16. entropy1

    The eye and pixels on a television screen

    How is it possible that when one watches a color television screen, one perceives the three base colors of the pixels as if it were a mix tone of these base frequencies, proportional to the relative intensity of the different pixels? It puzzles me! Hope someone knows how this is possible.
  17. O

    Medical Eye Floaters, Flashes and Seeing Spots in the Eye?

    The sudden appearance of a significant number of floaters, especially if they are accompanied by flashes of light in my eye for a few second. Does anyone know what is that? Thanks in advance for any suggestions
  18. Spinnor

    Dragon fly eye, lens very precise?

    Is the exact shape of the lens of a dragon fly ommatidium genetically encoded? I guess that the radius of curvature for both the front and back surfaces of the lens is somehow genetically encoded, call them r_f and f_b? I guess nature has come up with an optimal design for the dragonfly lens...
  19. W

    Intensity of light entering eye

    Hello all, I came across this question in mastering physics and simply could not solve it. I asked for the answer to the question and decided to move on.Homework Statement You are standing 1.7m from a 100-W lightbulb. If the pupil of your eye is a circle 5.0 mm in diameter, how much energy...
  20. M

    What happens if eye lens and objective lens are interchanged in

    What happens if eye lens and objective lens are interchanged in compound microscope? Also what about in astronomical telescope?
  21. D

    Corrective lenses, power of the eye change

    Ok so I'm doing my physics assignment on optics and have come to a point where i seriously need help. I need to talk about how a corrective lens, in particular contact lens, changes the optical power of the eye to suit different refractive errors. I need to know how a contact lens changes...
  22. J

    Medical How can I manage a career with eye floaters?

    Hi friends, sadly I have eye floaters, and I don't know what to do, I have some myopia and I've always had them but this year(I'm 20 years old) they seem to have become more. Do you have eye floaters? How do you cope with them? I'm a computer science student and I don't know how I will work...
  23. J

    Color Subtraction to the Eye Problem

    Yellow light shines on a sheet of paper containing a red pigment. We want to determine the color that we see. The obvious solution is this: Yellow can be though of as green and red light. Thus, green and red light can be though of striking the paper with red pigment. Red pigment absorbs...
  24. R

    Eye diagram on an oscilloscope

    I'm working on some stuff using an oscilloscope, and I need to figure out how to obtain an eye diagram, or eye pattern on it. Right now I just have a function generator hooked up to it. There's a sync output on the function generator as well as the output for the signal. Do I just hook up the...
  25. S

    Distance From Eye VS Visible Size

    Hi, this should be an easy question unless I'm not understanding it correctly. As an object gets closer to your eye, how does the "visible" size of the object increase. I'm thinking it can be modeled by either an inverse or inverse square function, but I don't know. Am I on the right path...
  26. B

    Best location for stars with naked eye

    These places seem great. Do places like these actually appear this way with the naked eye?
  27. P

    Eye vs Telescope: What Limits Our Sight?

    Hey guys, just wondering what limits how far an eye can see... I understand how an eye works. Light comes though the lens and focus on the retina, which goes to brain for interpretation, etc. And I understand the workings of different types of teloscopes. In different ways they gather...
  28. P

    Hi Guys,When the eye sees an object, there has to be light

    Hi Guys, When the eye sees an object, there has to be light reflecting from or emitting from the object itself. How does this happen with a hologram? Does the interference pattern actually scatter the light so we can see it?
  29. P

    Understanding Eye Floaters: Causes, Symptoms, and Treatment Options

    Eye floaters are debris in the eye's vitreous humour, which seem to float over your vision and are extremely annoying. When using an optical microscope my floaters become extremely clear against the bright background I am viewing, and what I see looks almost exactly like this...
  30. E

    What is the closest object that can be seen clearly with corrective glasses?

    Bill is farsighted and has a near point located 116 cm from his eyes. Anne is also farsighted, but her near point is 74.0 cm from her eyes. Both have glasses that correct their vision to a normal near point (25.0 cm from the eyes), and both wear glasses 2.0 cm from the eyes. Relative to the...
  31. M

    How does the human eye lens work?

    Ok, I know that the human eye lens adjusts its focal length depending on the object distance to obtain a sharp image on the retina because the image distance has to remain constant. What I am not able to understand is how do the ciliary muscles and the suspensory ligaments contract in order...
  32. D

    Schools Undergrad Math Electives (with an eye on Grad School)?

    Hello there, I'm currently an undergrad working towards a B.S. in Mathematics. I'm not too far along; I've completed the Calculus sequence and a couple classes after that. I'm currently in the equivalent of an "Intro to Proofs" class, required by my school. I work full-time, so during...
  33. M

    What happens to photons that don't get absorbed by a chromophore in the eye?

    I was explaining the physics of colors to someone in another forum, but I came to a point where I wasn't sure what happened next, what happens when a photon hits a chromophore in the eye and isn't the right energy to be absorbed by it. So, suppose a "green" photon hits a chromophore that...
  34. mugaliens

    News Eye on Americans - the FBI's Database on YOU

    Yes, that's right. Everything from privacy act material to your grades in high school and college, letters to the editor you wrote disagreeing with accepted government policy... Who knows what's really in the...
  35. A

    Medical Eye Lens Structure: Circular & Radial Fibres

    I just studied the structure of the lens of the eye. And I found out that there are two type of fibres present, which were the Circular Fibres and the Radial Fibres. Can anyone please tell me what is the purpose or function of these two fibres ? Or simply they are just fibres which are...
  36. G

    CERN scientists eye parallel universe breakthrough

    Interesting news. Thoughts?
  37. G

    Is my DIY laser rangefinder design eye safe?

    Hi all, I'd like some help calculating laser eye safety for a 905 nm diode laser system I'm building. It's for a scanning laser rangefinder and I need to figure out if my current design (a TOF rangefinder) can be feasibly be made Class 1 eye safe. The eye safety calculations are a little...
  38. H

    Eye Safety: Laser Diode Recommendations

    Can anyone recommend a good laser diode that won't cause damage to the eye with prolonged exposure?
  39. K

    Which is more sensitive: eye or fingertips?

    Which is more sensitive: eye or fingertips? P.S. touching or feeling
  40. J

    Distance between photons travelling from a bulb to your eye

    Homework Statement On a dark night, most people can see a 100W light bulb from at least 1 km away. Given that a 100W light bulb emits about 5W of visible light, and assuming that the wavelength is 500 nm, calculate the number of photons per second entering each eye (pupil diameter 0.7 cm) of...
  41. L

    Colors in white light visible to the naked eye?

    Hello, Simple question: Should they be visible to the naked eye? I googled it, but haven`t found any closely related material :) I`m really interested in this, but have no required knowledge to really answer this question nor explain it properly. Best Regards
  42. A

    Observing the Stark Effect in the Lab: Visible to the Eye?

    has somebody carried out stark effect experiment in the lab? is the effect visible to the eye or is it necessary to keep long exposures of the CCD to observe the effect?
  43. Mentallic

    Medical Sudden Eye Sight Loss: Causes & Treatment

    One night I couldn't sleep so I'm sitting there trying for hours and slowly drifting in and out, it was horrible. Anyway, by the morning I was really tired and dozing off wasn't a problem any more, but I was awoken at one point after a few hours sleep. After being awake for maybe 10 minutes, my...
  44. rhody

    The Mind’s New Eye: Frank Wilczek pub 04/10/2010

    Quotes from the article written up in http://www.cyprus-mail.com/opinions/mind-s-new-eye/20100410" by Frank Wilczek. From the brief writeup, there was nothing "new" or "unheard of" that stuck out, however the book may be filled with bits of information and/or insight that has not been heard...
  45. Mentallic

    Medical UV Rays & Eye Health - Is Tanning Safe?

    It's simply common sense that looking directly into the sun is a bad thing, but what about with your eyes shut? I'm unsure if the UV rays can penetrate the eyelid, or at least if they can, if a significant percentage of the rays get through. Is it a factor to consider when tanning for over an...
  46. K

    Range of Powers of Eye Lens - Optics Question

    Homework Statement The human eyeball is approximately spherical with a diameter of around 25mm. At the back of the eye is the retina, while at the front is a compound lens comprising the cornea (of fixed focal length) and the lens itself (with variable focal length), which can be...
  47. M

    Centripetal force in London Eye

    The centripetal force is caused by: Friction between seat & person or push of capsule wall on person. How come the answer is not the Tension in the cable?
  48. R

    Human Eye Optics: Near-Sightedness, Tree Image Distance & Height

    Homework Statement The far point of a nearsighted person is 6.0 m from her eyes, and she wears contacts that enable her to see distant objects clearly. A tree is 18.0 m away and 2.0 m high. (a) when she looks through the contacts at the tree, what is its image distance? (b) How high is the...
  49. A

    Medical Reading in dim light bad for eye

    here's the idea, i prefer to read in dim light because I'm suffering from migraine, but like 90% people around me keep telling that it will cause bad health in eye, but when i need the proves, they proofs nothing. So, maybe, i need to debunk this "old wives tales", and need some evidence...
  50. R

    Medical Why did my heart beat make the numbers on the screen look like ripples in water?

    Hey guys, That's my first post here, and I couldn't find any other place online where I can ask something like that and get rational scientific explanation. Here's what happened to me today and I have no idea what would cause it. I went to a coffee shop in afternoon to take a break from...
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