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PSYC 212 > Lecture 5: Light meets the eye > Flashcards

Lecture 5: Light meets the eye Flashcards

1
Q

What is light

A

Narrow band electromagnetic radiation that can be conceptualized as a wave or stream of photons

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2
Q

What is a photon

A

Quantum of visible light (or other form of em radiation) demonstrating both particle and wave properties

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3
Q

How do we consider light

A

Light as waveform when travels in space
Light as photon when hits retina and is transduced in neuronal activity

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4
Q

What is light refracted by

A

Cornea and lens

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5
Q

Describe light as electromagnetic wave

A

Em spectrum = characterized by frequency/speed of oscillations
Up rays, visible light, infrared radiation
Short 400nm = blue
Green/yellow = 500-600nm
700nm = longer, red/purple

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6
Q

Describe em wave

A

Electrical and magnetic part

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7
Q

When is light vertically polarized

A

Electric fields oscillation restricted to vertical plane = light is vertically polarized

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8
Q

What type of light do we usually experience

A

Mostly unpolarized
Bc every potential angel of polarity is equally present in most light sources

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9
Q

Describe polarizing glasses

A

Only let light pass with a certain polarity
Can be used to reduce total amount of light that reaches retina = sunglasses, or to present slightly diff visual info to right and left eye = modern 23 glasses (light of diff polarities to diff eyes)
Single wave = certain polarities

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10
Q

Describe a single ray of light

A

Electrical radiation = goes in one direction and oscillates
Perpendicular oscillation in magnetic field
= polarity/angle perpendicular to electromagnetic wave

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11
Q

Describe light scattering

A

Light hit small molecules
Redirect of Light as it interacts with molecules in medium = causes light to deviate from og path
Depends on size, shape and composition of particles relative to wavelength of light

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12
Q

Describe Rayleigh scattering

A

Scattering of light by particles much smaller than wavelength of light
Typically occurs in gasses, like sun light ray hits Moelecule oxygen = scatters
Causes shorter wavelengths (blue) to scatter more than longer wavelengths = why sky blue
Light scattered in all directions

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13
Q

Describe mie scattering

A

Scattering of light by particles that are comparable in size to wavelength of light
Like water drop, dust
Affects all wavelengths equally
Results in white/grayish appreance = clouds or haze
Maintains direction

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14
Q

Describe non selective scattering

A

Scattering of light by particles much larger than wavelength of light
Like water droplets in fog
Affects all wavelengths equally
Result in uniform white appearance
Larger molecules and direction bit less affected than mie

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15
Q

What types of scattering Can happen when light hits larger molecule

A

Mie or non selective

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16
Q

Describe light absorption

A

Process by which ligth energy taken up by material - converts it into other forms of energy
Like heat,
Rather than it being trasnmitted or reflected, like when light hits skin = disappears bc turned into heat
Ligth interacts with surface
Usually light hits object = some absorbed and reflected

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17
Q

Describe light reflection

A

Light bounces off surface of a material
Reflection can be specular or diffuse

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18
Q

Describe specular reflection

A

Light reflects off smooth surface in a single predictable direction
All ligth redirected in same direction
Like mirror or still water

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19
Q

Describe diffuse reflection

A

Ligth reflects off rough surface
Scatter in many directions

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20
Q

Define light transmission

A

Passage of ligth through material
Light continues to propagate without being absorbed or reflected

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21
Q

Define light refraction

A

Bending of light as it passes from one medium to another with a different refractive index
Changes speed and direction of light

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22
Q

Name layers that light goes through eye in order

A

Cornea
Anterior chamber
Pupil
Lens
Vitreous humor
Retina
Choroid
Sclera

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23
Q

Define cornea

A

Transparent
Dome shaped
Outer layer at front of eye
Helps focus ligth on retina

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24
Q

Define anterior chamber

A

Fluid filled space betwene cornea and iris
Contains aqueous humour = nourishes cornea and lens

25
Define pupil
Circular opening in Center of iris Regulates amount of light entering eye Acts as diaphragm Attached to ciliary muscle via zonular fibres Behind pupil = lens, refract and redirect light on retina (fovea)
26
Define vitreous humour
Clear gel like substance Fills space between lens and retina Helps maintain eye shape and transmit light to retina
27
Define choroid
Behind retina Vascular layer betwene retina and sclera Provides oxygen and nutrients to outer layers of retina
28
Define sclera
Tough, outer layer of eye Provides structural support and protection Whites of eye
29
Define retina
Thin Light sensitive tissue lining back of eye Where photoreceptor cells - rods and cones Convert light into neural signals for visual processing (nerve fibres = process light)
30
What is optical infinity
Objects at a distance of 20 feet (6 meters) or more from eye = at optical infinity Do not require accommodation to be seen distinctly by a healthy eye
31
Emmetropia
Ligth rays coming from objects at optical infinity are naturally focused on retain without any anomalies Lens in relaxed state, focuses light
32
Accommodation
Process by which eyes lens changes shape Controlled by ciliary muscles - to focus light on retina for clear vision at diff distances Refract light more, divergent angle, light ray more divergent - not parallel
33
Focal length
Distance between optical Center of a lens and its focal point Where parallel rays of light converge or appear to diverge Determines lens magnifying power and ability to focus on objects at various distances
34
What is focal point
Goal = refract light, converge them on focal point = Center of retina - light get focused here
35
What are eye problems
Bc capacity of lens to focus light on retina not good enough
36
Describe presbyopia
Age related Eye gradually loses ability to focus on nearby objects Caused by reduction of elasticity of lens - and weakening fo eye ciliary muscles = limit ability of eye to accommodate for near vision ~40 y/o Lens stiffer, usually need to accommodate for close objects but lens cannot shrink enough, light focused behind retina,cannot perceive properly
37
Describe hyperopia
Farsightedness Refractive error where distance objects appear clearer than near ones Bc light focuses behind retina Eyeball too short Lens fine
38
Describe myopia
Nearsightedness Refractive error Near objects appear clearer than distant ones bc ligth focuses in front of retina Often due to longer eyeball, problem with objects at optical infinity
39
Describe astigmatism
Refractive error causes by irregularly shaped cornea or lens Leads to distorted or blurred vision at all distances because light focused unevenly on retina Lens cannot focus light on one focal point, so looks kinda blurred
40
What does blue light do
Stimulate receptors in retina that control sleep/wake cycles Photopigemnt = melanopsin
41
Describe Hermann con Helmholtz
1821-1894 Physicist and pshyiologust Amazed by how poor an eye is = bad design, lose lots of info “PERCEPTION IS UNCONSCIOUS INFERENCE” BRAIN makes up rest, agreed with Kant = neo kantian = more scientific interpretation of Kant theory’s
42
Describe blind spot - gen
Area in visual field = close to centre, bit to right of visual field - do not see anything, brain makes up for it Dot will dissapear, brain can fill in yellow in line Brain makes you percieve it = brain guesses
43
Describe blind spot - procedure
Close left eye Look at cross with right eye Bring closer to eyes while looking at cross When 30-40cm from screen = YELLOW DOT DISSAppears If move right eye = will reappear Move back to cross = dissapear That spot of visual field wehre see nothing= blind spot
44
Name parts of retina
Fundus Optic disc Macula Fovea
45
Descrube fundus of retina
Back of eye Interior surface of eye Visible through Ophthalmascope Includes retina, optic disc, macula, blood vessels
46
Describe optic disc of retina
Region wehre optic nerve exits eye Contains no photoreceptor cells Creates blind spot Area where blood vessels that feed the retina enter eye and where axons fo retinal ganglion cells merge into optic nerve (origin of optic nerve)
47
Describe macula of retina
Centra area of retina responsible for detailed central vision, critical for tasks like reading and recognizing faces Macula = area that contains high density of photoreceptors, almost no blood vessels Darker spot
48
Describe fovea of retina
Small, central depression within macula that contains high concentration of CONE CELLS Provides sharpest visual acuity and colour vision Inside macula Depression
49
Describe image of fovea
Capillary - bv in front Bipolar cells, then photoreceptors then pigment epithelium (Need to be close to for regeneration of piegmtns) So fovea dips down to here, all other cells pushed aside = most ligth enters, v high density cones = accurate vision
50
Describe photo receptors and angle from fovea graph
Nose side and temple side = mostly rods, so like evryehwere Except = fovea, has most cones Optic disk = no rods or cones=blind spot
51
What is fovea used for
See things with high precision in tiny fraction visual field
52
Describe central vision
Tasks that require high visual acuity Like reading Limited to visual angle of 2-3 degrees No more than width of thumbnail when viewed at arms length - 57cm in front of us Cannot see things very well, seems like we can bc keep moving eyes
53
Define visual acuity
Clarity or sharpness of vision Measured by ability to discern fine details, typically evaluated using standardized eye charts
54
Define visual angle
Angle forms by an object at the eye Determined by objects size and distance form observer Used to quantify how large an object appears in the field of view
55
Describe ganglion cells
Ligth hits this first Neurons located in retina that receive visual info from bipolar cells and transmit it to brain via their axons = form optic nerve Convey info to brain
56
Describe bipolar cells
Light hit second 2 polarities Intermediate neurons in retina = connect photoreceptors (rods and cones) to ganglion cells Transmit visual signals from outer to inner retina Synapse with photoreceptors and ganglion cells
57
Describe photoreceptors
Light hit third Rods and cones Specialized cells in retina that detect light and convert it into electrical signals
58
Define rods
Sensitive to low light levels Responsible for vision in dim lighting (scotopic vision) = v sensitive but not accurate, night time
59
Define cones
Active in bright light Responsible for colour vision and fine detail (photopic vision)

PSYC 212 (18 decks)

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