shouldn't the distance of the image depend on the distance of the object? (1/f= 1/di + 1/do) so why does the light focus at one point, and not even a focal plane since all light entering the eye isnt parallel to the principle axis.
2006-12-25 09:45:47 · 7 answers · asked by doverbeach 3 in Science & Mathematics ➔ Physics
The eye fortunately has a flexible lens that adjusts to focus what you want to see. The centre of vision, fovea I think it is called is small and that is the area that gets focused. The rest of the eye is peripheral vision and it is not important to be in focus.
Of course the older people here would contradict that the eye focusses every time! Our lenses get less flexible with age.
2006-12-25 09:51:35 · answer #1 · answered by Anonymous · 0⤊ 0⤋
This happens because the shape of the lens adjusts to bring the images into focus. Once the object is beyond a certain distance, it is functionally the same as infinity as far as optics is concerned. A mountain 5 miles away can be focused by the same lens as the moon. On the other hand, inside about 15 inches, the human lens can no longer accomodate.
2006-12-25 10:39:01 · answer #2 · answered by Jerry P 6 · 0⤊ 0⤋
Unfortunately, t doesn't always.
Although there are muscles that involuntarially change the shape and focal length of the lens, sometimes it isn't enough. When the lens focuses is in front of the retina, it is nearsightedness and when it would be behind, it is farsightedness. Glasses can correct this.
As people age, the lens becomes less flexible and the muscles become unable to change the focus. Then people must wear bi/trifocals or variable focus lenses to correct the focus.
2006-12-25 11:09:44 · answer #3 · answered by Anonymous · 0⤊ 0⤋
Red eye is due to light bouncing off the cornea. That can be avoided two ways. First of all if you are shooting with red eye reduction on, the camera will shoot a pre-flash. The pre-flash is intended to dilate the pupil. If you aren't getting two flashes when in red eye mode, then it isn't working right. Pros avoid the red eye by having the flash a greater distance from the lens. That way the light does not bounce from the flash, to the cornea, back to the camera. You either need to move the flash up (about 4-6" minimum) or get your red eye flash mode to work properly. If the person who are shooting has slow pupils the red eye reduction won't work with them. Fortunately many picture editing packages have easy red-eye elimination. Basically you circle the eye and tell it to remove the red-eye...
2016-05-23 06:19:21 · answer #4 · answered by Anonymous · 0⤊ 0⤋
Yes, the f of our eye can be adjusted rapidly. Also, the image forms on the retina, thats all. Its not the focal plane always. Its the focal plane only when u see someone standing v.far away.
2006-12-25 10:36:57 · answer #5 · answered by Venkat 3 · 0⤊ 0⤋
Yes, the lens of the eye is flexible, and muscles adjust its shape to change its focal length. Your brain makes this adjustment automatically, so that whatever is at your center of view is in focus. It's not important for things outside your center of view to be in focus at the same time. If you need for something in your peripheral field of view to be in focus, you look at it, and then your brain focuses on that. This is a feat even the best cameras can't duplicate.
2006-12-25 17:22:56 · answer #6 · answered by Frank N 7 · 0⤊ 0⤋
with the help of the ciliary muscles
2006-12-25 10:00:59 · answer #7 · answered by raj 7 · 0⤊ 0⤋