Chapter 6 Human Vision

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Oswald Lang
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1 Chapter 6 Notes: Human Vision Name: Block:

2 Human Vision The Humane Eye: 8) 1) 2) 9) 10) 4) 5) 11) 12) 3) 13) 6) 7)

3 Functions of the Eye: 1) Cornea a transparent tissue the iris and pupil; provides most of the focussing 2) Aqueous Humour a fluid that fills the front chamber of the eye 3) Pupil a dark, transparent region in the centre of the eye where light 4) Iris a coloured ring of surrounding the pupil 5) Lens a flexible structure behind the pupil and iris; fine tunes the focus by automatically changing its shape 6) Suspensory Ligaments attaches the to the ciliary muscle 7) Ciliary Muscle attaches to the suspensory 8) Sclera the tough, white layer of the eye 9) Choroid the layer of blood found between the sclera and retina 10) Retina the inner lining of the back of the eye containing light-sensitive and 11) Fovea an area concentrated in ; responsible for sharp vision 12) Vitreous Humour the -like fluid that fills the space of the eyeball 13) Optic Nerve the nerve that connects the eye to the Pathway of Light Through the Eye: Forming an Image: Cornea -light is focused at the back of the eye. The image formed on the retina is but your brain interprets the image as being

4 The Blind Spot: blind spot -the area where the optic nerve enters the retina is called the blind -it cannot detect light because of the absence of both and Rods and Cones: Special cells in the retina called and convert light into electrical signals that are sent to the brain via the nerve. Function Sensitivity Types Pigment Response Size Quantity Location Rod Cells -used for vision (black-and-white) - light sensitive - type of light-sensitive pigment -have pigment than cones, so can detect less light - response to light - than cone cells -about million in the human eye -mostly found on the edges of the retina Cone Cells -used for illumination vision (colour) - very light sensitive - types of light-sensitive pigment (red, green, and blue) -have pigment than rods, so require more light - response to light - than rod cells -about million in the human eye -mostly found in the of the retina

Vision Problems: 1) Near-sightedness (myopia) the ability to see nearby objects clearly but objects are unfocused uncorrected corrected with concave lens -image falls short of retina (eye has shape

unfocused uncorrected corrected with convex lens -image falls behind retina (eye has shape than normal eye) -convex lens is used to the parallel rays slightly to allow image to fall on retina 3)

5 Vision Problems: 1) Near-sightedness (myopia) the ability to see nearby objects clearly but objects are unfocused uncorrected corrected with concave lens -image falls short of retina (eye has shape than normal eye) -concave lens is used to the parallel rays slightly to allow image to fall on retina 2) Far-sightedness (hyperopia) the ability to see distant objects clearly but objects are unfocused uncorrected corrected with convex lens -image falls behind retina (eye has shape than normal eye) -convex lens is used to the parallel rays slightly to allow image to fall on retina 3) Astigmatism blurred vision uncorrected -image falls behind and in front of retina (eye has irregularly shaped ) 4) Types of Blindness a) Blindness the inability or difficulty in detecting. b) Snow Blindness the temporary partial or complete blindness caused by overexposure to the of sunlight on snow. c) Night Blindness the inability to see in light due to injury or malnutrition. d) Colour Blindness the inability to see or between colours.

$Extending Human Vision 1) Compound Microscope -uses two lenses with relatively short focal lengths to focus light from small, close objects 2) Refracting Telescopes -uses two lenses to view distant$ 5) Cameras -light passes through a lens and focuses the image on a light detector 6) Laser Surgery -the light waves in laser light have the same and travel with their crests and troughs aligned -used

5) Cameras -light passes through a lens and focuses the image on a light detector 6) Laser Surgery -the light waves in laser light have the same and travel with their crests and troughs aligned -used

6 Extending Human Vision 1) Compound Microscope -uses two lenses with relatively short focal lengths to focus light from small, close objects 2) Refracting Telescopes -uses two lenses to view distant objects 3) Reflecting Telescopes -uses a mirror, a plane mirror, and a convex lens to focus light from distant objects 4) Binoculars -uses two telescopes mounted side by side. 5) Cameras -light passes through a lens and focuses the image on a light detector 6) Laser Surgery -the light waves in laser light have the same and travel with their crests and troughs aligned -used to remove cataracts, re-attach retinas, stop bleeding, and reshape 7) Optical Fibres -transparent glass fibres that can light from one place to another -make use of total internal (light is reflected continuously from the sides) -used in telecommunications (e.g. telephone, video, and internet signals)

7 Flashcards 1) 2) What are the parts of the eye? What is the pathway of light through the eye? 3) 4) What orientation is the image on the retina? What is the blind spot? 5) 6) What are rods and cones? What is nearsightedness? 7) 8) What is farsightedness? What is astigmatism?

8 9) 10) What are the different types of blindness? What is a compound microscope? 11) 12) What is a refracting telescope? What is a reflecting telescope? 13) 14) What are binoculars? What are cameras? 15) 16) What is laser surgery? What are optical fibres?

sclera pupil What happens to light that enters the eye?

sclera pupil What happens to light that enters the eye? Human Vision Textbook pages 202 215 Before You Read Some people can see things clearly from a great distance. Other people can see things clearly only when they are nearby. Why might this be? Write your