Human Factors- Vision

Question 1

amplitude of wave =

wavelength of wave =

Answer 1

• perceived as brightness

- perceived as hue

Question 2

light is ____________ _______ that is visible to our eyes

Answer 2

electromagnetic radiation

Question 3

smaller wave length =

• order of colour from small wavelength to large
• what wavelength colour do we perceive the strongest
• wavelength colour impacts meletonin

Answer 3

the higher the energy of the wave and the further it will travel

• blue- green-yellow-red
• green
• blue

Question 4

______ is the change in direction of propagation of a wave due to a change in its transmission medium

Answer 4

refraction

Question 5

A lens that can focus parallel light rays to a point 1 meter from its axis has a refractive power of
- what is the refractive power of our eyes when viewing distant objects (48 from the cornea)

Answer 5

1 diopter

- 59 diopters

Question 6

what changes our focal distance?

- the higher the diopter the _____ the refraction

Answer 6

the lens

- greater

Question 7

when light enters the eye it is refracted through the ____ and the ____ and focused on the ____

Answer 7

• cornea, lens, retina

Question 8

how do we adjust the amount of light entering the eye

Answer 8

the pupil dilates and constricts

Question 9

o focus for near objects we need to increase the refractive power of the lens- this is called?

Answer 9

accommodation

Question 10

how do we accommodate?

• what does this cause?
• when relaxed, the _______ ______ pull the lens back into a thinner flatter shape

Answer 10

Contraction of the Ciliary Muscle enables the lens to become rounder and have more refractive power

• fatigue causing
• suspensory ligament

Question 11

how many diopters of accommodation do we have?

- what happens with age? (what is it called)

Answer 11

15 diopters of accommodation

- decreases with age - presbyopia

Question 12

is accommodation an instantaneous experience?

Answer 12

no, you can experience temporarily with a sudden change in gaze

Question 13

light focused in front of the retina is called? this is corrected with?
light focused behind the retina is called? this is corrected with?

Answer 13

• myopia, concave lens

- hypermetropia, convex lens

Question 14

if you have astigmitism you rely on ______ process to _____

Answer 14

cognitive processes to accomodate

Question 15

what gets strained when squinting to see something, dim lighting, fatigue etc

Answer 15

ciliary muscles

Question 16

Refractive error due to an unequal curvature of the refractive surface (either cornea and/ or lens)

Answer 16

astigmatism

Question 17

Outer regions of the lens focus light at a point slightly ahead of the mid portion of the lens. This causes vision to be blurred

Answer 17

spherical aberration

Question 18

a typical eye has ____ microns of spherical aberration

- spherical aberration is reduced to ____ microns –> see it more clear

Answer 18

+0.15

+ 0.04

Question 19

Objects that are very close require muscular contraction to enable the eyes to ____ (and focus via accommodation) on the object

Answer 19

converge

Question 20

Excessive convergence at a work station causes ?

Answer 20

fatigue and muscle imbalances to occur, making the task more difficult and causing strain

Question 21

downward gaze requires ____ vergence than an upward gaze

Answer 21

less

Question 22

3 things to do when working with near object:

Answer 22

• minimize required vergence (closer then put it lower)
• minimize the required accommodation (have to accommodate more when we gaze down)
• avoid accommodation traps
  (objects right at the point of accommodation will cause them to constantly adjust in and out of focus)

Question 23

sharpness of vision, measured by ability to discern letters or numbers at given distance according to fixed standard, discriminate fine detail

Answer 23

visual acuity

Question 24

visual acuity is dependent on ?

Answer 24

accommodation

Question 25

checkerboard, letter target, landhold ring, parallel bars are example of what type of test

Answer 25

acuity measures

Question 26

what does a vision of 20/40 mean?

Answer 26

that a person can detect a critical detail at 20 feet that a person with normal vision could detect at 40 feet

Question 27

region of light sensitive receptors

Answer 27

the retina

Question 28

2 types of receptors and what they are sensitive to and how man are there

Answer 28

rods: light sensitive and responsible for night vision (120 mill) cones: color sensitive cells densely located in the fovea provide photopic vision (6 mill)

Question 29

central pit composed of closely packed cones in the eye in the centre of the macula responsible for sharp central vision. Necessary for visual detail reading and driving

Answer 29

the fovea central

Question 30

___ types of cone types with different sensitivity to _______, any giving colour is perceive by the ________ of firings, Colour blindness is if ___ set of cells is missing

Answer 30

3, wavelengths distributions one

Question 31

- what percent of people have normal vision | - what percent of people have deuteranomaly

Answer 31

- 92% | - 2.7%

Question 32

- Protanopia (< 1% of males) see in shades of? - Deuteranopia (<1% of males) see in shades of? - tritanomaly/tritanopia (very rare); _____-_______ deficiency blindness - monochromacy (extremely rare):

Answer 32

- blue and yellow - blue and yellow - blue/yellow - inability to distinguish any colour

Question 33

rods are mostly distributed where? | - this means we cant do what in the periphery

Answer 33

- in the periphery | - cant identify colour well in our periphery and have less acuity

Question 34

across the colour spectrum we are most sensitive to ? and least sensitive to?

Answer 34

- green, blue/green | - pure red and blue

Question 35

we need very little _____ light to detect differences

Answer 35

green

Question 36

we can illuminate a room or sign with this color and not worry about bleaching out our ability to see in dark environments

Answer 36

red

Question 37

as we switch from cone to rod vision (day to night), shorter wavelengths appear brighter (green objects appear brighter, red objects appear darker

Answer 37

purkinje shift

Question 38

at night we see primarily with the ____ in our eyes and they are indeed more sensitive to all kinds of light than are the _____ which we use primarily for daylight

Answer 38

rods, cones

Question 39

our most sensitive light ranges are ______-_____ light during the day and _____ at night

Answer 39

- yellowish green | - green

Question 40

at night sensitive to ___ is near zero

Answer 40

red

Question 41

____ ____ ____Contain melanopsin which is Sensitive to blue light and Can modify our circadian rhythm (releases melatonin)

Answer 41

retinal ganglion cells

Question 42

light _____ and ______ of exposure determine the impact of self- luminous tablets on melatonin suppression --> greatest effect after ___ hours

Answer 42

level, duration | --> 2 hours (not after 1)

Question 43

- total light emitted by a source: - light falling onto a surface: - light reflected by a surface:

Answer 43

- luminous flux - illuminance - luminance

Question 44

what are the units for lumination/illuminance?

Answer 44

lux

Question 45

a common candle emits light with roughly ___cd luminous intensity

Answer 45

1

Question 46

common health effects associated with poor lighting include:

Answer 46

- headache and eyestrain - neck, back, and shoulder - -> when staining to see items because poor lighting - falling, tripping, slipping - dropping materials or tools - depression

Question 47

the main causes of lighting problems are:

Answer 47

Insufficient light •  not enough light for the need •  Glare - too much light for the need •  Improper contrast •  Poor distribution, and •  Flicker

Question 48

how does lighting effect performance?

Answer 48

- performance time decreases with increasing amounts of illumination - errors decrease as well

Question 49

what is the difference between direct glare and indirect glare

Answer 49

- light sources in the field (direct) | - light sources (reflect, light sources outside the field)

Question 50

2 types of indirect glare

Answer 50

- specular (smooth surface) | - Diffuse (matte surface - a white wall)

Question 51

what are the effects of glare on the work place?

Answer 51

1. Discomfort: annoyance or pain causing discomfort, no change in performance 2. disability: reduction in ability to perform task, phototropis- natural tendency to gaze at bright objects, transient adaptation- change in contrast 3. blinding

Question 52

natural tendency to stare at bright lights

Answer 52

phototropism

Question 53

3 ways to reduce display reflection

Answer 53

- indirect lighting system - blinds/drapes - low wattage direct light on documents

Question 54

in unpolarized light, which is most of the light we see, the fluctuations in the electric field are ? - when light hits a flat surface such as water or the road, some of it become horizontally polarized, which causes glare

Answer 54

random- occur in all directions - only safe, vertically polarized light passes through specifically treated polarized lens (only vertical wave lengths get through)

Question 55

polarized lenses have been chemically treated with a compound whose molecules naturally align parallel to one another, absorbing light and creating a ?

Answer 55

microscopic polarization filter

Question 56

ppl can see lights flashing on and off up to to about ? hz

Answer 56

50 hz (50 flashes per second)

Question 57

what are the light flicker health effects

Answer 57

flourecent lights, complaints about headaches, eye strain and general eye discomfort

Question 58

When compared to regular fluorescent lights with magnetic ballasts, the use of high frequency electronic ballasts (20,000Hz+) in fluorescent lights resulted in more than a___% drop in complaints of eye strain and headaches

Answer 58

50

Question 59

we basically can only identify colors we can _____ | - why are russions better at separating out blues ?

Answer 59

name | - they have more categories for blue "siniy" "goluboy"