Chapter 2

Question 1

What is the visible spectrum for humans?

Answer 1

400 to 700 nanometers

Question 2

What is brightness in terms of perceptual dimensions?

Answer 2

Intensity of light

Question 3

What is colour in terms of perceptual dimensions?

Answer 3

Dominant wavelength of light

Question 4

Define absorption of light.

Answer 4

Energy that is taken up and not transmitted at all.

Question 5

Define scattering of light.

Answer 5

Energy dispersed in an irregular fashion; much of it is absorbed or scattered before reaching the perceiver.

Question 6

Define reflection of light.

Answer 6

Energy redirected when it strikes a surface, usually back to its point of origin.

Question 7

Define transmission of light.

Answer 7

Energy passed on through a surface (neither reflected nor absorbed).

Question 8

Define refraction of light.

Answer 8

Energy altered as it passes into another medium (e.g., light entering water from air).

Question 9

What are the three pairs of muscles controlling eye movement responsible for?

Answer 9

Controlling direction and coordination of eye movement.

Question 10

What is the sclera?

Answer 10

The ‘white’ of the eye; tough protective coating.

Question 11

What is the cornea?

Answer 11

Transparent membrane where light first enters the eye.

Question 12

What is the iris?

Answer 12

Coloured muscle controlling the size of the pupil.

Question 13

What is the pupil?

Answer 13

Opening in the iris controlling the amount of light entering the eye.

Question 14

What is the lens?

Answer 14

Controls how much light is refracted, focusing the image on the retina.

Question 15

What is the retina?

Answer 15

Contains photoreceptors that transduce light into neural signals.

Question 16

What happens to the iris and pupil in bright light?

Answer 16

Iris contracts → pupil constricts.

Question 17

What happens to the iris and pupil in dim light?

Answer 17

Iris relaxes → pupil dilates.

Question 18

What are the two main types of photoreceptors?

Answer 18

Rods and cones.

Question 19

What do rods specialize in?

Answer 19

Night vision; high sensitivity; no colour processing.

Question 20

What do cones specialize in?

Answer 20

Daylight vision; fine visual acuity; colour perception.

Question 21

Name the three types of cones.

Answer 21

S-cones (blue), M-cones (green), L-cones (red).

Question 22

Where are cones concentrated?

Answer 22

In the fovea.

Question 23

Where are rods concentrated?

Answer 23

Outside the fovea; absent in the fovea.

Question 24

What is the optic disk?

Answer 24

Area where optic nerve and blood vessels exit the eye; no photoreceptors → blind spot.

Question 25

What percentage of focusing is done by the cornea and aqueous fluid?

Answer 25

About 80%.

Question 26

What percentage of focusing is done by the lens?

Answer 26

About 20%.

Question 27

What is accommodation?

Answer 27

Lens thickens via ciliary muscles to focus on near objects.

Question 28

What is emmetropia?

Answer 28

Normal vision; no refractive error.

Question 29

What is myopia?

Answer 29

Nearsightedness; light focuses in front of retina.

Question 30

What is hyperopia?

Answer 30

Farsightedness; light focuses behind retina.

Question 31

What is presbyopia?

Answer 31

Age-related farsightedness due to lens hardening and weakened ciliary muscles.

Question 32

What is astigmatism?

Answer 32

Unequal curvature of cornea or lens causing blurred vision.

Question 33

What is retinitis pigmentosa?

Answer 33

Degeneration of rods first → night blindness; may progress to total blindness.

Question 34

What is macular degeneration?

Answer 34

Loss of central vision due to destruction of macula.

Question 35

Where does sensory transduction occur?

Answer 35

In rods and cones; light → neural code via photopigment change.

Question 36

What are horizontal cells?

Answer 36

Cells connecting photoreceptors and bipolar cells horizontally.

Question 37

What are bipolar cells?

Answer 37

Transmit signals from rods/cones to ganglion cells.

Question 38

What are amacrine cells?

Answer 38

Synapse between bipolar and ganglion cells; modulate signals.

Question 39

What are ganglion cells?

Answer 39

Output neurons of the retina; axons form optic nerve.

Question 40

What pathway do parvo ganglion cells belong to?

Answer 40

Parvocellular pathway; colour and fine detail (high spatial, low temporal resolution).

Question 41

What pathway do magno ganglion cells belong to?

Answer 41

Magnocellular pathway; motion (high temporal, low spatial resolution).

Question 42

What is lateral inhibition?

Answer 42

Inhibition of neighbouring neurons to enhance contrast and edge detection.

Question 43

What is convergence?

Answer 43

Multiple photoreceptors synapsing onto one bipolar/ganglion cell.

Question 44

What does high convergence cause?

Answer 44

Higher sensitivity, lower acuity (e.g., rods).

Question 45

What does low convergence cause?

Answer 45

Higher acuity, lower sensitivity (e.g., cones in fovea).

Question 46

What are Mach bands?

Answer 46

Illusory bright or dark lines at gradient boundaries due to lateral inhibition.

Question 47

What is simultaneous contrast?

Answer 47

Perceived brightness/colour of an area changes with surrounding brightness.

Question 48

What is visual acuity?

Answer 48

The smallest spatial detail that can be resolved (resolution).

Question 49

What is visual angle?

Answer 49

Measurement of object size on retina in degrees; distance-dependent.

Question 50

What is spatial frequency?

Answer 50

Number of light-dark cycles per degree of visual angle.

Question 51

What is Fourier analysis?

Answer 51

Mathematical method decomposing signals into sine waves.

Question 52

What is contrast sensitivity?

Answer 52

Ability to detect differences in luminance between areas.