Module 18

Question 1

how does light travel

Answer 1

• in waves
• through air, empty space, and some liquids and solids

Question 2

amplitude for light

Answer 2

• intensity of energy
• determines the brightness of light

Question 3

wavelength in light

Answer 3

• length in space of each cycle of the wave
• determines the hue of light

Question 4

frequency

Answer 4

• how fast the wave cycles
• measure in Hz (cycles per second)
• inversely related to wavelength

Question 5

two light waves

Answer 5

• light is made of two waves at 90° angles from each other
• one is magnetic and the other is electrical

Question 6

the electromagnetic spectrum

Answer 6

• visible light is only a small portion of waves that exist
• light is a linear spectrum, but we perceive it as a circle
• combine red and violet frequencies to make magenta

Question 7

lense

Answer 7

• focuses light

Question 8

cornea

Answer 8

• protective layer
• helps focus light in towards the eye

Question 9

pupil

Answer 9

• lets light into the eye
• appears black from outside

Question 10

iris

Answer 10

• muscle that makes the pupil dialate
• adjusts for the amount of light coming in
• colored part of the eye

Question 11

optical nerve

Answer 11

• transmits visual information to the brain
• creates a blind spot in the eye because no photoreceptors

Question 12

fovea

Answer 12

• focal point in the retina

Question 13

retina

Answer 13

• layer of photoreceptors in the eye

Question 14

the visual pathway

Answer 14

• light that hits the right side of the eye goes to the right side of the brain (comes from left)
• has to do with where in the eye the light hits, not which eye

Question 15

animals that don’t have a blind spot

Answer 15

• cephalopods (octopi)
• photoreceptors are in front of the neurons they connect to so the retina doesn’t need a hole for the optic nerve

Question 16

two types of photoreceptors in the retina

Answer 16

cones and rods

Question 17

rods

Answer 17

• night vision
• motion
• more in periphery
• more sensitive to light and motion

Question 18

cones

Answer 18

• allow color perception
• more in fovea
• short, medium, and long wavelength receptive cones

Question 19

three cone types

Answer 19

• for short, medium, and long wavelengths
• ratios of firing rates between different cone types tell us the hues of light
• no single cone type on its own gives us color information

Question 20

how color vision deficiency occurs

Answer 20

• “colorblindness”
• one cone type is absent
• one cone type isn’t fully functional
• has a tuning curve that is not sufficiently different from another cone type
• most common involves lack of sensation of redness vs. greenness

Question 21

Helmholtz’s trichromatic theory of color perception

Answer 21

• any color can be represented (at least approximately) as a combination of red, green, and blue light
• light color is additive

Question 22

opponent process theory of color perception

Answer 22

• red vs. green
• yellow vs. blue
• white vs. black
• demonstrated by negative afterimages
  
  • desensitization to a color increases sensitivity to the opposite color

Question 23

opponent processing of motion

Answer 23

-waterfall illusion
- desensitization to unchanging direction of motion causes aftereffect of perceived motion in the opposite direction

Question 24

monocular depth perception

Answer 24

• only one eye needed
• cues include size and height
  
  • determines closeness to the horizon
• linear perspective
  
  • parallel lines converge in the visual field as they get farther away
• texture gradient
  
  • textures appear more densely packed, less spread out and detailed when they are farther away
• atmospheric/Ariel perspective (haze)
  
  • more distant objects look fainter, blurrier, and bluer
• relative motion
  
  • when youre moving, closer objects move across your visual field faster than distant objects
• interposition/occlusion

Question 25

binocular depth cues

Answer 25

• require two eyes at once
• binocular/retinal disparity
  
  • the farther away an object is, the more similar its position on the two retinas
• convergence
  
  • how much you have to cross your eyes to focus on the object

Question 26

feature detectors

Answer 26

neurons that respond to specific features, such as shape, angle, and movement

Question 27

parallel processing

Answer 27

• different aspects of an object are processed in different brain areas and then integrated into a whole

Question 28

color and light constancy

Answer 28

• the brain adjusts our perception of color to keep colors constant under different lighting conditions
• simplifies perception in the real world