VISION & THE VISION & THE EYEBALLEYEBALL

I.I. The Stimulus Input – Light The Stimulus Input – Light EnergyEnergy

A. A. What Strikes our Eye?What Strikes our Eye?

Electromagnetic EnergyElectromagnetic Energy

Pulses of EME are seen as colorPulses of EME are seen as color

B.B. Electromagnetic SpectrumElectromagnetic Spectrum1.1. Gamma Rays – short Gamma Rays – short

(imperceptible)(imperceptible)

2.2. Visible Light – narrow but Visible Light – narrow but perceptibleperceptible

3.3. Radio Waves – long (imperceptible)Radio Waves – long (imperceptible)

C.C. Physical Characteristics of LightPhysical Characteristics of Light

1. Wavelength – distance from 1. Wavelength – distance from one one peak to the next (COLOR)peak to the next (COLOR)

2. Intensity – amount of energy 2. Intensity – amount of energy in in the wave, or height the wave, or height (BRIGHTNESS)(BRIGHTNESS)

THE EYETHE EYE

A.A. Physical StructuresPhysical Structures

1. CORNEA – clear protective 1. CORNEA – clear protective covering of the eyecovering of the eye

2. IRIS – colored muscle that 2. IRIS – colored muscle that opens opens and closes to control and closes to control amount of amount of light entering the light entering the eyeeye

3. PUPIL – little black opening 3. PUPIL – little black opening that that changes size depending changes size depending on on movement of the Irismovement of the Iris

4.4. LENS – located behind the LENS – located behind the pupil, pupil, and focuses the and focuses the incoming rays onto incoming rays onto the retinathe retina

5.5. OPTIC NERVE – band of OPTIC NERVE – band of neural neural fibers in the back of the fibers in the back of the eye, carry eye, carry impulses to the impulses to the occipital lobeoccipital lobe

B. THE RETINAB. THE RETINA

surface of the inner eye that is surface of the inner eye that is sensitive to light and contains the sensitive to light and contains the receptor Rods and Conesreceptor Rods and Cones

1. RODS – visual receptors that are 1. RODS – visual receptors that are used for vision in low light used for vision in low light

2. CONES – visual receptors that 2. CONES – visual receptors that are used for vision in lighted areas are used for vision in lighted areas (color)(color)

3.3. BLIND SPOT – where the optic BLIND SPOT – where the optic nerve leaves the eye, place with nerve leaves the eye, place with no visual receptorsno visual receptors

4.4. FOVEA – the point of central focus FOVEA – the point of central focus that contains only a high that contains only a high concentration of conesconcentration of cones

FUN FACTFUN FACT

““cat vision” as it is called, is given its name due cat vision” as it is called, is given its name due to cats have excessive amounts of rods (night to cats have excessive amounts of rods (night vision) and a larger pupil in which to enter vision) and a larger pupil in which to enter more light during the nightmore light during the night

C. VISUAL INFORMATIONC. VISUAL INFORMATION

1.1. ACUITY – sharpness of vision is ACUITY – sharpness of vision is affected by distortions in the shape affected by distortions in the shape of the eyeof the eye

2.2. NEARSIGHTEDNESS – objects NEARSIGHTEDNESS – objects from a distance are focused in from a distance are focused in front of the retina producing front of the retina producing blurred vision – resulting from an blurred vision – resulting from an eye that is too longeye that is too long

3.3. FARSIGHTEDNESS – rays from FARSIGHTEDNESS – rays from nearby objects are not focused until nearby objects are not focused until past the retina producing blurred past the retina producing blurred vision. Results from eyeball that is vision. Results from eyeball that is too short.too short.

III. COLOR VISIONIII. COLOR VISION

A.A. Is a tomato Red?Is a tomato Red?

1. NO! It reflects the red 1. NO! It reflects the red wavelengthswavelengths

2. The “color” is our mental 2. The “color” is our mental constructionconstruction

B.B. Detecting ColorDetecting Color

1. we have color cones for only 1. we have color cones for only three colors (red, blue, green)three colors (red, blue, green)

2. we can discriminate some 7 2. we can discriminate some 7 million different colors all based million different colors all based on red, blue, and greenon red, blue, and green

C. Color-Deficiency (color blindness)C. Color-Deficiency (color blindness)

1.1. about 1 in 50 people are color about 1 in 50 people are color blindblind

2.2. most are male – sex linked most are male – sex linked genegene

3.3. color deficiency only occurs in color deficiency only occurs in red red or green conesor green cones

D. AfterimagesD. Afterimages1.1. staring at one color for an staring at one color for an extended period of time will result extended period of time will result in that colors opponent when in that colors opponent when moving vision to white moving vision to white background.background.

2.2. referred to as opponent referred to as opponent process process theorytheory