4.2 Seeing

Question 1

electromagnetic energy

Answer 1

pulses of energy waves that can carry information from place to place

Question 2

wavelength

Answer 2

the distance between one wave peak and the next wave peak

Question 3

visible spectrum

Answer 3

our eyes detect only the range from about 400 to 700 billionths of a meter

Question 4

cornea

Answer 4

a clear covering that protects the eye and begins to focus the incoming light

Question 5

pupil

Answer 5

a small opening in the center of the eye

Question 6

iris

Answer 6

the colored part of the eye that controls the size of the pupil by constricting or dilating in response to light intensity

Question 7

lens

Answer 7

a structure that focuses the incoming light on the retina

Question 8

retina

Answer 8

the layer of tissue at the back of the eye that contains photoreceptor cells

Question 9

visual accomodation

Answer 9

the process of changing the curvature of the lens to keep the light entering the eye focused on the retina

Question 10

nearsighted

Answer 10

if focus is in front of retina

Question 11

farsighted

Answer 11

the focus is behind the retina

Question 12

optic nerve

Answer 12

a collection of millions of ganglion neurons that sends vast amounts of visual information, via the thalamus, to the brain

Question 13

Rods

Answer 13

visual neurons that specialize in detecting black, white, and gray colors

Question 14

Cones

Answer 14

visual neurons that are specialized in detecting fine detail and colors

Question 15

fovea

Answer 15

which is the central point of the retina

Question 16

blindspot

Answer 16

there are no photoreceptor cells at the place where the optic nerve leaves the retina

Question 17

feature detector neurons

Answer 17

specialized neurons, located in the visual cortex, that respond to the strength, angles, shapes, edges, and movements of a visual stimulus

Question 18

hue

Answer 18

• the shade of a color
• conveyed by the wavelength of the light that enters the eye (we see shorter wavelengths as more blue and longer wavelengths as more red)

Question 19

intensity

Answer 19

height of the wave (bigger or more intense waves are perceived as brighter)

Question 20

Hermann von Helmholtz (1821–1894)

Answer 20

he theorized that color is perceived because the cones in the retina come in three types

Question 21

Young-Helmholtz trichromatic color theory

Answer 21

what color we see depends on the mix of the signals from the three types of cones

Question 22

color blindness

Answer 22

the inability to detect either green and/or red colors

Question 23

opponent-process color theory

Answer 23

proposes that we analyze sensory information not in terms of three colors but rather in three sets of “ opponent colors‖: red-green, yellow-blue, and whiteblack

Question 24

gestalt

Answer 24

a meaningfully organized whole

Question 25

Depth perception

Answer 25

the ability to perceive three-dimensional space and to accurately judge distance

Question 26

visual cliff

Answer 26

a mechanism that gives the perception of a dangerous drop-off, in which infants can be safely tested for their perception of depth

Question 27

depth cues

Answer 27

messages from our bodies and the external environment that supply us with information about space and distance

Question 28

Binocular depth cues

Answer 28

depth cues that are created by retinal image disparity—that is, the space between our eyes, and thus which require the coordination of both eyes

Question 29

convergence

Answer 29

the inward turning of our eyes that is required to focus on objects that are less than about 50 feet away from us

Question 30

Monocular depth cues

Answer 30

depth cues that help us perceive depth using only one eye

Question 31

beta effect refers

Answer 31

the perception of motion that occurs when different images are presented next to each other in succession

Question 32

phi phenomenon

Answer 32

we perceive a sensation of motion caused by the appearance and disappearance of objects that are near each other