The Eye
Function, Structure, Focus, Vision
Correction
The Ear vs. The Eye
Mechanical Sound Waves
with frequency range of
20-20,000 Hz
• Focus (pinna focuses
sound waves down ear
canal)
• Transfer (ear drum
vibrates and causes the 3
tiny bones to vibrate)
• Interpret (cochlea
resonates)
• Send Signals (aural
nerves send impulses to
the brain
Non-Mechanical
Electromagnetic Waves in
the Visible Light Range
(4.3 x 1014 to 7.9 x 1014 Hz)
• Focus (Cornea refracts
light: initial focus through
fixed convex lens)
• Transfer (through the
pupil with 2nd refraction
through lens (moveable)
• Interpret (light transferred
to retina: cone cells color)
• Send Signals (optic nerve
sends impulses to the
brain)
Stare at bird for 30 s and look to left—what color is the ghost image?
Stare at bird for 30 s and look to left—what color is the ghost image?
• Cyan (blue light + green light)
• Your red cone receptors
are fatigued, so you
only perceive cyan.
The Eye and its Structure
•
•
•
Focusing lenses (double convex lens system)
– Cornea (convex lens)--main focusing, fixed
– Lens (convex lens)—fine focusing, adjusts
Pupil (light regulator)
Retina (back of eye)
– Rod cells (senses intensity)
– Cone cells (red, green
and blue light receptors)
Rods and Cones in the Retina
• Retina (back of eye)
– Rod cells (senses intensity)
– Cone cells (red, green and blue light receptors)
Photochemical Reaction produced when
frequencies of visible light are absorbed
Rods and Cones in the Retina
• Retina (back of eye)
– Rod cells (senses intensity)
– Cone cells (red, green and blue light receptors)
Photochemical Reaction produced when
frequencies of visible light are absorbed—peak
at red green and blue, but produce all colors
based upon intensity as well as frequency
Rods and Cones
• http://www.accessexcellence.org/AE/AEC/
CC/vision_background.html
• http://webvision.med.utah.edu/photo1.html
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Colors:additive and subtractive
• http://mysite.verizon.net/vzeoacw1/colorsu
b.html
• http://mysite.verizon.net/vzeoacw1/colorad
d.html
The Eye and its Structure
•
•
•
Focusing lenses (double convex lens system)
– Cornea (convex lens)--main focusing, fixed
– Lens (convex lens)—fine focusing, adjusts
Pupil (light regulator)
Retina (back of eye)
– Rod cells (senses intensity)
– Cone cells (red, green
and blue light receptors)
Rods and Cones
• http://www.accessexcellence.org/AE/AEC/
CC/vision_background.html
• http://webvision.med.utah.edu/photo1.html
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What is color?
• When we see color, we are seeing specific
frequencies of visible light
• VISIBLE LIGHT IS ROYGBIV
• Red, orange, yellow, green, blue, indigo and
violet
• For visible light
– Red has the lowest frequency and longest
wavelength
– Violet has the highest frequency and shortest
wavelength
28.2 Color by Reflection
a.
b.
This square reflects all the colors illuminating it. In sunlight, it is white.
When illuminated with blue light, it is blue.
This square absorbs all the colors illuminating it. In sunlight it is
warmer than the white square.
Why a shirt appears blue.
• A blue shirt appears blue in white light because
it reflects only blue and absorbs red and green
(or the other colors)
• A blue shirt appears black in red light because it
absorbs red and reflects nothing.
• A blue shirt appears blue in blue light because is
reflects blue.
• A white shirt appears blue in blue light because
it can reflect blue light.
Why a shirt appears blue.
• A blue shirt appears blue in white light because
it reflects only blue and absorbs red and green
(or the other colors)
• A blue shirt appears black in red light because it
absorbs red and reflects nothing.
• A blue shirt appears blue in blue light because is
reflects blue.
• A white shirt appears blue in blue light because
it can reflect blue light.
Colorblindness
• Colorblindness is a deficiency in the
number of red, green or blue cones (too
few of one or more cone types).
Normal vision
Colorblindness
http://www.toledo-bend.com/colorblind/aboutCB.html
http://www.colblindor.com/2008/10/02/color-blindness-simulator-newtool-released-on-colblindor/
Better Eyes
• http://micro.magnet.fsu.edu/primer/java/hu
manvision/accommodation/index.html
Rods and Cones
• http://users.rcn.com/jkimball.ma.ultranet/Bi
ologyPages/V/Vision.html
What is color?
• When we see color, we are seeing specific
frequencies of visible light
• VISIBLE LIGHT IS ROYGBIV
• Red, orange, yellow, green, blue, indigo and
violet
• For visible light
– Red has the lowest frequency and longest
wavelength
– Violet has the highest frequency and shortest
wavelength
28.1 The Color Spectrum
When sunlight passes through a prism, it separates into a spectrum of all the
colors of the rainbow.
roygbiv
The pupil regulates the intensity
of light entering the eye
The retina contains rod and cone cells
that are photosensitive to different
frequencies of visible light. Red-greenblue cone cells are the color receptors
Both the cornea and inner lens are convex
(convergent) lenses
30.6 The Eye
Inner lens moves to
focus close up and far
away images
Concave lens
Convex lens
Vision correction
Corrected by divergent (concave) lens
Corrected by convergent (convex) lens
Concave lens
Convex lens
http://www.ghi.com/yourhealth/encyclopedi
a/articles/color_blindness_basics.html
http://micro.magnet.fsu.edu/primer/java/hu
manvision/accommodation/index.html
CONCAVE AND CONVEX
MIRRORS
Concave mirror causes
light rays to diverge.
Convex mirror
causes light rays to
converge.