What is Eyes: Definition and 127 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. G

    Explain Humor in "Haddocks Eyes" for Alice in Wonderland Fans

    Could someone explain the humor in "Haddocks Eyes" - (for Alice in Wonderland fans)? Hello , I was recently reminded of a section of 'Through The Looking Glass' - the one about Haddock's Eyes because of a post here at PF :- I will post the relevant material :- Well , I understood the humor...
  2. Q

    Seeing Is Believing: Is It Possible?

    is this possible?
  3. Dotini

    Human Eyes See Cosmic Bubbles that Algorithms Miss

    I thought this story was charming, since it hints that there still might be a few things people can do that computers cannot (yet) do. I have no idea of the significance of these bubbles, but I'd be interested to hear others comments...
  4. D

    Why doesn't intense infrared radiation from a fire harm your eyes?

    The other night I was watching a campfire and the infrared light from it was intense enough that it warmed my face quite a bit, almost uncomfortably. I must have been receiving quite a bit of invisible light in my eyes, but there was no damage (and I've never heard any warning about watching...
  5. T

    Can someone please cast their eyes over these questions on thermodynamics

    Hello all, i am haveing a few issues with a thermodynamics/thermal problem and was wondering if someone could lend a fresh set of eyes to it. Homework Statement a gas is contained in a cylinder with a frictionless piston the helium is compressed quasistatically from an initial state where...
  6. C

    Medical Does closing your eyes conserve energy?

    I'm no scientician, so I was wondering if your eyes not getting any light would actually decrease the amount of energy you'd be using?
  7. N

    Photons observed on photographic plate - but not in eyes? Why?

    Hey, We can observe the build up of photons on a photographic plate, but we can't observe this build up with our bare eyes. i.e. without needing a photographic plate - just by looking like how we look right now. how come?
  8. A

    What is the size of the image of a tree on a man's retina?

    Homework Statement A man looks at a tree of height 20.0m a distance of 300m away. the cornea has a radius of curvature of 7.7mm, eye has refractive index of 1.47 and the length of the eye is 24.0mm. Calculate the size of the image of the tree on the man's retina. Homework Equations...
  9. P

    Translation: God's heaven in my mother's eyes

    Hello, can anyone help me translate this into latin? i really need help and it is urgent. thanks, already.
  10. Y

    Color Difference between Left and Right Eyes?

    Hello, I am new to Physics forums :) Anyways, I have noticed that there is a very slight color difference (Hue) between my two eyes, unnoticeable when both are open. I close my right eye, and looking with my left eye, I see that all the colors are slightly "warmer" (More intense, all the...
  11. R

    Are There Safe Laser Pointers for Eye Use in Clubs and Shows?

    Are their laser pointers that are totally safe for the eyes? What kind to look for?
  12. T

    Watch someone's life through their eyes

    Kinda like "Being John Malkovitch" but not quite. My scenario deals with historical figures that are dead. What if it were possible to relive someone elses life, watch it on a tv perhaps, AND hear their thoughts as they thought them... We have Einstien's brain somewhere, right? If it were...
  13. D

    Question about sticky eyes (communication)

    I've read a few books on how to improve communication and social skills, but I noticed some disperaties. In one book, it said that the more you can apply sticky eyes (not taking your eyes off the person) the better. In another book, it said avoid sticky eyes, because it will make the other...
  14. Saladsamurai

    Are my eyes burning from eating red chillies?

    So recently I have been cooking with red chillies for the first time in my life. I also wear contact lenses. Within a day or two of my chili binge, I have noticed that when I put my contacts in in the morning, my eyes burn like hell. I know that it is related to the chillies. The thing is, I...
  15. J

    Optics question - eyes and cameras, and the mythical 50mm lens

    Eyes and cameras - a topic that has been troubling me Hi all. This is my first post. I'm seriously thinking about applying to optometric college in the fall. I'm trying to improve my knowledge as much as possible of the area, and one question that keeps coming up (I'm a hobby photographer...)...
  16. J

    What's that stuff around your eyes?

    "well, that's kinda . . . is there anyway . . . I mean . . . why exactly . . . just what exactly is all that stuf around your eyes?" "dad! it's makeup. Don't you like it?" "well, it's kinda' a lot don't you think?" "dad, I think it looks nice." "yeah, well . . . how about nothing...
  17. M

    Why does our brain invert the image received from our eyes?

    There's really no such thing as "upside down" in an absolute sense, only relative to what we're used to. Why then does our brain invert the image? What's wrong with leaving it the way it is?
  18. R

    How does eyes encodes information to be sent to brain?

    Is there anyone who knows on how's the information being transferred from eyes to brain? I'm not asking about how a single optical nerve works here, but how does these nerves arranged so that they can convey a 'live video' from eyes to brain. Is it a matrix of optic nerves with a single nerve...
  19. DaveC426913

    Medical Can modern glass eyes be moved like natural eyes?

    Can glass eye sporters move their glass eye similar to their good eye? Or are modern glass eyes still immobile?
  20. G

    Calculating Focal Length of Human Eye When Focusing Closely

    The focal length of a relaxed human eye is approximately 1.78 cm. When we focus our eyes on a close-up object, we can change the refractive power of the eye by about 16 diopters. Calculate the focal length of the eye when we focus closely. 1/di+1/do=1/f im not really sure what to...
  21. S

    Grease under the eyes of football players - dumb or not?

    Grease under the eyes of football players -- dumb or not? Maybe this is silly question, but why do football players put grease under their eyes? I've always assumed that it's supposed to reduce glare, but this seems to make little sense considering the angle of the incident light, which mostly...
  22. H

    LHC: Multimillion God's Particle Chase & Earth's Extinction Rate

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  23. X

    What could be causing the strange vision changes in my eyes?

    I have had headaches for goodness knows how long, but this week its has been none stop and more on my left side. Just above my eyebrow. Yesterday I saw a weird site in my eyes, like a black and white calidiscope which moved as my eyes did. It got progressivly bigger and the middle became almost...
  24. fluidistic

    Medical Is this normal (about my eyes)

    When I fold a little bit my eyes and I look at a luminous source (like a light bulb or a window if there's sun outside), I see many spherical shapes and sometimes shapes like wires. I'm nearsighted but strangely I see quite well how the shapes are defined. Furthermore when I move my eyes the...
  25. D

    Are the eyes an example of the photoelectric effect

    It seems to me that the eyes are an example of the photoelectric effect at work. If so, which is more effective; current technology, photosynthesis, or our eyes?
  26. K

    How can our eyes differentiate distance?

    All photons that we see hit our eyes, so how do our eyes know where they came from?
  27. M

    Odds in Probability of Green Eyes

    Homework Statement Of 27 students in a class, 11 have blue eyes, 13 have brown eyes, 3 have green eyes. If 3 students are chosen at random what are the odds of the following occurring? Only 1 has green eyes.Homework Equations Odds = P( s )/P( f ) = P( s )/( 1 - P( s )) Probability success = P(...
  28. I

    Identifying three identical metal bars (with your eyes closed )

    Identifying three identical metal bars (with your eyes closed!) Homework Statement How would you determine, non-destructively, and with eyes closed, which is which amongst three identically-shaped metal bars known to consist of a permanent magnet, a piece of soft iron and a piece of copper...
  29. T

    Laser Pointer Wave Energy and eyes seeing

    Homework Statement A typical “laser pen” pointer has a power output of 3mW at 670nm. If the angular divergence of the beam is 2mrad, estimate the maximum distance at which it could be seen by a day-adapted human eye. You can assume that in bright light, a normal eye will give a signal from...
  30. W

    Sensitive Eyes? Solutions for Photoshoots with Flash

    Whenever I have my picture taken, the flash of the camera blinds me. I close my eyes as a result (involuntarily) and come out with the eyes closed in the photograph while other people in the same picture maintain open eyes. This happens all the time. Is there any way to help this situation?
  31. glondor

    What Should I Look For When Getting My Eyes Checked?

    aaarg I think I need to get my eyes checked...pahhh. I have noticed over the last few months the vision in my left eye is a lil fuzzy and my depth perception is fading a bit. Not so good in my line of work. I have not had the eyes checked in years and I was wondering what new and exciting things...
  32. K

    Optics - For what distance must we focus our eyes to see this image

    An object is placed 1m in front of a plane mirror. An observer stands 3m behind the object. For what distance must the observer focus his eyes in order to see the image of the object?
  33. B

    Medical Can Laser Eye Surgery Correct Cross Eyes in Adults?

    Can laser eye surgery/anything fix cross eyes? 2 of my friends are cross-eyed and they're adults ty
  34. P

    Medical Is the monitor (of your PC) destroying your eyes?

    Is the monitor (of your PC) "destroying" your eyes? Hello! :smile: I have one question for you. Is the monitor (of your PC) "destroying" your eyes? Are there any research or statistics relating this question? Thank you.
  35. S

    Dance of Magnetic Fields Exposed to Human Eyes

    Unfortunately, magnetic fields are by their nature invisible, but scientists from NASA’s Space Sciences Laboratory have managed to put on film what these natural phenomenons would look like if we could see them with our own eyes. Please note that this is a simulation and has been created using...
  36. Holocene

    Look at a mole. They have eyes, but they are small, and often

    Look at a mole. They have eyes, but they are small, and often completely covered by fur. I'm not a biologist, but I'd venture to guess that many are completely blind. If this is a design from an intelligent being, all I can say is WTF?
  37. ZapperZ

    VOTE Photo Contest - A Sight For Sore Eyes

    All of the pictures submitted this week are sights for sore eyes. So well done to everyone who participated. Please vote for the picture that best represents our theme this week. Administrative update: I have selected MK to run the PF Photo Contest for the few weeks that I had mentioned earlier...
  38. ZapperZ

    PF PHOTO CONTEST - A Sight For Sore Eyes (4/12-4/18)

    A Sight For Sore Eyes Do you think you have a picture that, when someone sees it, he/she would say "Now that's a sight for sore eyes!"? If you do, then that picture fits our theme this week. Zz. Contest Rules: 1. Any digital photo or digitally-scanned photo relevant to the theme will be...
  39. rohanprabhu

    Please reply the moment ur eyes read this

    how long do eggs [hen's eggs] take to boil? I'm boiling 4 eggs.. fully immersed in water and on high gas.. and since I've already started it.. i need to know how much time will it take to get hard boiled. please reply as quick as u can.. i'll be refreshing this page now :D
  40. M

    What is the Limit of FPS Our Eyes See & Why?

    Does anyone have a good explanation of what fields per second our eyes see, and why it is at that? By why I don't mean evolutionary features, I mean optically, such as beyond a certain fps the our biological singular value decomposition does not not amount to much, something physics or mathy.
  41. M

    Solving Punnet Squares for Dark Hair & Brown Eyes

    [SOLVED] Punnet Squares The allele for dark hair D is dominant over that of red hair d, and the allele for brown eyes B is dominant over that of blue eyes b. A women is red-haired and has blue eyes. Her husband is dark-haired and has brown eyes. a) What are the possible genotypes for the...
  42. Mk

    Do Human Eyes Grow? - Exploring the Cuteness Factor

    Do human eyes grow? I was thinking this might be a reason why people think big eyes are "cute," if babies were born with the same size eyes they have when they are old.
  43. K

    Can Autogenic Training and Visualization Exercises Improve Your Vision?

    do any of yo know any ways to improve your vision other than laser eye surgery and corrective contacts? i've heard of eye exercises like this :uhh: but my optometrist said that was mainly a relaxation thing, it won't repair your eyes
  44. P

    What is more strenuous on eyes, reading on a computer screen or text?

    Which is more strenuous on human eyes? Because i do plenty a lot of both of them. If i learn that one is less strenuous than the other, i wil probably start spending more time doing that instead. Btw, i have an LCD monitor, which I've heard is better than a regular monitor, but it kind of just...
  45. C

    Can I Get an Alternative Skin for a White Background?

    My poor lil eyes. O.o I love to hangout here but white text on white background is really killing my eyes. Can I please please please get an option for an alternative skin with white background? :bugeye:
  46. R

    What if eyes were sensitive to infrared?

    if eyes were sensitive to infrared, what would happen? the environment would appear brighter/duller or we would be able to see farther than normal or sun would be invisible? What do you think?
  47. P

    Can eye exercises help combat study fatigue?

    I find the biggest obstacle I have to putting in long hours of hard studying is my eyes. Does anyone else have this problem? And what do you do to combat it? Personally, I go out for walks and runs. But are there other ways? Does anyone do eye excercises? Do they work? I am short sighted and...
  48. P

    Comparing Camera & Human Eyes: Zoom & Focus

    Is a camera very much like a normal (i.e. perfect vision) eye? If we wear lenses, we will like the camera be able to 'see' focused images very far away or very close which is like zooming in or out with the camera. Some people with eye problems like myopia cannot see a focused image beyond...
  49. Q_Goest

    How do bacteria use vision for survival and adaptation?

    From Quantum Evolution (Johnjoe McFadden) 1. What biological feature of a bacteria allows it to 'see' or detect a given wavelength of light? What part of or feature of the cell detects light of a given wavelength? 2. Are these not single celled organisms? 3. How common is this feature?
  50. R

    Do Our Eyes Limit Our Understanding of Other Dimensions?

    I'm getting tired of reading about how some people think other physical dimensions would have to be seen with the eyes in order to exist. The way other dimensions are being conceptualized is inhibiting understanding of the subject. To use a popular phrase, those working in the field need...
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