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

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/colorsub.html

• http://mysite.verizon.net/vzeoacw1/coloradd.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

a. This square reflects all the colors illuminating it. In sunlight, it is white. When illuminated with blue light, it is blue.

b. This square absorbs all the colors illuminating it. In sunlight it is warmer than the white square.

28.2 Color by Reflection

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-new-tool-released-on-colblindor/

                                                           

Better Eyes

• http://micro.magnet.fsu.edu/primer/java/humanvision/accommodation/index.html

Rods and Cones

• http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/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

When sunlight passes through a prism, it separates into a spectrum of all the colors of the rainbow.

28.1 The Color Spectrum

roygbiv

Both the cornea and inner lens are convex (convergent) lensesThe retina contains rod and cone cells

that are photosensitive to different frequencies of visible light. Red-green-blue cone cells are the color receptors

The pupil regulates the intensity of light entering the eye

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/encyclopedia/articles/color_blindness_basics.html

http://micro.magnet.fsu.edu/primer/java/humanvision/accommodation/index.html

Concave mirror causes light rays to diverge.

Convex mirror causes light rays to converge.

CONCAVE AND CONVEX MIRRORS