VISION & THE EYEBALL

The Stimulus Input – Light Energy A. What Strikes our Eye?

Electromagnetic Energy Pulses of EME are seen as color

Electromagnetic Spectrum Gamma Rays – short (imperceptible) Visible Light – narrow but perceptible Radio Waves – long (imperceptible)

Physical Characteristics of Light 1. Wavelength – distance from one peak to the next (COLOR) 2. Intensity – amount of energy in the wave, or height (BRIGHTNESS)

THE EYE Physical Structures 1. CORNEA – clear protective covering of the eye 2. IRIS – colored muscle that opens and closes to control amount of light entering the eye

3. PUPIL – little black opening that. changes size depending on 3. PUPIL – little black opening that changes size depending on movement of the Iris 4. LENS – located behind the pupil, and focuses the incoming rays onto the retina

5. OPTIC NERVE – band of neural. fibers in the back of the eye, carry 5. OPTIC NERVE – band of neural fibers in the back of the eye, carry impulses to the occipital lobe

B. THE RETINA surface of the inner eye that is sensitive to light and contains the receptor Rods and Cones 1. RODS – visual receptors that are used for vision in low light 2. CONES – visual receptors that are used for vision in lighted areas (color)

BLIND SPOT – where the optic nerve leaves the eye, place with no visual receptors FOVEA – the point of central focus that contains only a high concentration of cones

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

C. VISUAL INFORMATION ACUITY – sharpness of vision is affected by distortions in the shape of the eye

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

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

III. COLOR VISION Is a tomato Red? 1. NO! It reflects the red wavelengths 2. The “color” is our mental construction

Detecting Color 1. we have color cones for only three colors (red, blue, green) 2. we can discriminate some 7 million different colors all based on red, blue, and green

C. Color-Deficiency (color blindness) 1. about 1 in 50 people are color blind 2. most are male – sex linked gene 3. color deficiency only occurs in red or green cones

2. referred to as opponent process theory D. Afterimages 1. staring at one color for an extended period of time will result in that colors opponent when moving vision to white background. 2. referred to as opponent process theory