Chapter 4 Terms, Summary & Review Questions

Question 1

Accommodation of the Lens

Answer 1

adjustment of the thickness of the lens to focus on objects at different distances

Question 2

Blind Spot

Answer 2

retinal area where the optic nerve exits

Question 3

Brightness Contrast

Answer 3

increase or decrease in an objects apparent brightness by comparison to objects around it

Question 4

Color Constancy

Answer 4

tendency of an object to appear nearly the same color under a variety of lighting conditions

Question 5

Cone

Answer 5

visual receptors adapted for color vision, daytime vision, and detailed vision

Question 6

Cornea

Answer 6

rigid, transparent structure on the surface of the eyeball

Question 7

Dark Adaptation

Answer 7

gradual improvement in the ability to see in dim light

Question 8

Electromagnetic Spectrum

Answer 8

continuum of all the frequencies of radiated energy

Question 9

Fovea

Answer 9

central area of the human retina

Question 10

Ganglion Cells

Answer 10

neurons in the eye that receive input from bipolar cells, which in turn receive input from the visual receptors

Question 11

Iris

Answer 11

colored structure on the surface of the eye surrounding the pupil

Question 12

Lens

Answer 12

flexible structure that varies its thickness to adjust its focus on objects at different distances

Question 13

Negative Afterimage

Answer 13

perception of new colors after the removal of other ones

Question 14

Opponent-Process Theory

Answer 14

theory that we perceive color in terms of a system of paired opposites: red versus green, yellow versus blue, and white versus black

Question 15

Optic Nerve

Answer 15

set of ganglion cell axons that turn around and exit the eye

Question 16

Perception

Answer 16

interpretation of sensory information

Question 17

Pupil

Answer 17

adjustable opening in the eye

Question 18

Receptor

Answer 18

specialized cell that converts environmental energies into signals for the nervous system

Question 19

Retina

Answer 19

layer of visual receptors covering the back surface of the eyeball

Question 20

Retinex Theory

Answer 20

concept that the cerebral cortex compares the patterns of light coming from different parts of the retina and synthesizes a color perception for each area

Question 21

Rod

Answer 21

visual receptors that are adapted for vision in dim light

Question 22

Sensation

Answer 22

conversion of energy from the environment into a pattern of response by the nervous system

Question 23

Stimulus

Answer 23

energy from the world that affects us in some way

Question 24

Trichromatic Theory (or Young-Helmholtz theory)

Answer 24

theory that color vision depends on the relative rate of response of three types of cones

Question 25

You may have heard people say that cats can see in total darkness. Is that possible?

A- Yes, they send rays out of their eyes that enable them to see in the dark.
B- Yes, they see in the dark, although no one knows how they do it.
C- Dont be ridiculous. Vision is the detection of light, so vision in darkness is impossible.

Answer 25

C- Dont be ridiculous. Vision is the detection of light, so vision in darkness is impossible.

Question 26

Why do we have our most detailed vision from the part of the retina called the fovea?

A- The fovea has the greatest density of receptors.
B- The lens and cornea focus light most clearly on the fovea.
C- The fovea is the point most distant from the blind spot.
D- The fovea has an equal ratio of cones and rods.

Answer 26

A- The fovea has the greatest density of receptors.

Question 27

Why do we detect faint light more effectively in the periphery of the retina than in the fovea?

A- The periphery has more tightly packed receptors.
B- The center of the retina is in the shadow of the pupil.
C-The periphery of the retina has more cones, which are more sensitive to faint light.
D- In the periphery, more receptors converge their output onto the next cell

Answer 27

D- In the periphery, more receptors converge their output onto the next cell

Question 28

After light stimulates receptors at the back of your retina, where do the receptors send their output?

A- Directly to the thalamus
B- Directly to the cerebral cortex
C- To other neurons that are closer to the center of the eye

Answer 28

C- To other neurons that are closer to the center of the eye

Question 29

What fills the blind spot of the retina?

A- The lens
B- The fovea
C- A bone
D- Axons and blood vessels

Answer 29

D- Axons and blood vessels

Question 30

According to the trichromatic theory, how does our nervous system tell the difference between bright yellow-green and dim yellow-green light?

A- By the relative rates of response by medium-wavelength and long-wavelength cones
B-By the relative rates of response by medium-wavelength and short-wavelength cones
C-By the relative rates of response by all three types of cones
D- By the total amount of activity by all three types of cones

Answer 30

D- By the total amount of activity by all three types of cones

Question 31

Which of these phenomena does the opponent-process theory explain better than the trichromatic theory does?

A- The tendency of an objects apparent color to change depending on variations in the objects surrounding it
B-The fact that color vision is better in the fovea than in the periphery
C- Negative color afterimages
D- The fact that people can mix three colors of light to match any other color

Answer 31

C- Negative color afterimages

Question 32

Which of these phenomena does the retinex theory explain better than the trichromatic theory or the opponent-process theory does?

A- The tendency of an objects apparent color to change depending on variations in the objects surrounding it
B-The fact that color vision is better in the fovea than in the periphery
C-Negative color afterimages
D-The fact that people can mix three colors of light to match any other color

Answer 32

A- The tendency of an objects apparent color to change depending on variations in the objects surrounding it

Question 33

How vision works.

Answer 33

Vision occurs when light rays strike the retina at the back of the eye, causing cells to send messages to the brain. We do not send sight rays out of the eyes.

Question 34

Light

Answer 34

Light is the part of the electromagnetic spectrum that excites receptors in the eyes. If we had different types of receptors, we would define other wavelengths as light.

Question 35

Focus

Answer 35

The cornea and lens focus light onto the retina.

Question 36

Cones and Tods.

Answer 36

Cones, found mainly in and near the fovea, are essential for color vision. Rods, more numerous toward the periphery, detect dim light.

Question 37

Blind spot.

Answer 37

The blind spot is the area of the retina through which the optic nerve exits.

Question 38

Color vision.

Answer 38

Color vision depends on three types of cones, each sensitive to a particular range of light wavelengths. Cones transmit messages so that later cells in the visual system indicate one color (e.g., blue) by an increase in activity and another color (e.g., yellow) by a decrease. The cerebral cortex compares responses from different parts of the retina to determine color experiences.

Question 39

Color vision deficiency.

Answer 39

Complete color-blindness is rare. Certain people have difficulty distinguishing reds from greens for genetic reasons.