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30 Cards in this Set

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electromagnetic radiation

long wave length =
short energy (Infrared, Radio Wave)
electromagnetic radiation

short wave length =
high energy (Gamma rays, X-rays, UV light)
wave-photon duality
light travels in wave-like fashion with "single packets" of energy called photons
visible spectrum
different colors of light have different wavelengths
Violet
380nm
Blue
480nm
Green
550nm
Yellow
630nm
Orange
680nm
Red
730nm
color of an object
determined by which wavelengths are REFLECTED back to the retina (not absorbed by the object)
white
all wavelengths reflected by object
black
all wavelengths absorbed by object
light refraction
light will bend when it passes from one medium (air) into another (lens) e.g. pencil in glass of water
convex lens
(thicker at center, tapered at edge) causes light to bend so that it comes together at a focal point
real image
image at focal point of convex lens --> inverted & reversed
focusing light on the retina

cornea
constant (unchanging) refraction
focusing light on the retina

lens
can change refraction and focal length; ciliary muscles change convexity of the lens
Focusing for Distance Vision

far point of vision
distance beyond which lens will not change its shape (about 20 feet) (flattest point of the lens)
Focusing for Distance Vision

emmetropic eye
normal, healthy eye
Focusing for Close Vision
(Less than 6 feet)

accommodation of lens
lens shape becomes more convex, light rays bend more sharply, shorter focal length for the closer object (ciliary muscles for lens)
Focusing for Close Vision
(Less than 6 feet)

near point of vision
shortest distance for focusing (maximum convexity of lens); about 8-10 inches; gets worse with age
Focusing for Close Vision
(Less than 6 feet)

presbyopia
poor close vision in elderly; inelasticity of the lens
Focusing for Close Vision
(Less than 6 feet)

accommodation of pupils
constriction of pupils; better focus, less divergent rays (constrictor muscles of iris)
Focusing for Close Vision
(Less than 6 feet)

convergence of eyes
eyes rotate medially to keep image on center of the retina (medial rectus muscles of eyeballs)
Vision Problems Related to Refraction

myopia ("nearsighted")
distant objects are blurred; distant objects are focused in front of the retina, rather than directly on it
Vision Problems Related to Refraction
myopia ("nearsighted")

causes
eyeball too long; lens too strong

concave lens can correct light before eye
Vision Problems Related to Refraction

hyperopia ("farsightedness")
close objects are blurred; close objects are focused beyond the retina, rather than directly on it
Vision Problems Related to Refraction

hyperopia ("farsightedness")

Causes
a. eyeball too short; poor refraction of a lens

b. convex lens can correct light before eye
Vision Problems Related to Refraction

astigmatism
- blurry images at all distances; unequal curves on lens and/or cornea, creating discontinuous image on the retina