GASB05H3 Chapter Notes - Chapter 30-50: Stephen Kuffler, Beta-Carotene, Micrograph
Chapter 2: The First Steps in Vision: From Light to Neural Signals
A Little Light Physics:
-2 ways to conceptualize light:
oWave: an oscillation that travels through a medium by transferring energy from
one particle or point to another without causing any permanent displacement of
the medium
oPhoton: quantum of visible
light or other form of
electromagnetic radiation
demonstrating both particle
and wave properties
-Pathway of light from star to eye:
oElectromagnetic radiation from
a star travels in a straight line
at the 186, 000 miles/per
oWhen it reaches atmosphere,
photons are absorbed by dust,
vaporized water, and more
oSome light gets diffracted/scattered by particles
oRest of photons, will hit the surface of the object
oIf light hits light-colored surface = reflected
oLight hits dark-colored surface = absorbed
oIf light isn’t reflected/absorbed = transmitted
oReflect: to redirect something that strikes a surface – light, sound, or heat –
usually back forward its point of origin
oTransmit: to convey something (e.g. light) from one place or thing to another
oRefract:
1. Alter the course of a wave of energy that passes into something from
another medium
2. To measure the degree of refraction in a lens or eye
oEx. When determines how much the light must be bent by eyeglasses for it to be
properly focused on the retina = refraction
find more resources at oneclass.com
find more resources at oneclass.com
Eyes That Capture Light:
oFuck this image
othe image below shows a front-to-
back slice through a human eye
-the cornea is the first tissue that the light
touches
oCornea: the transparent “Window”
in the eyeball
othe cornea provides a window to the world because it is transparent (photons are
transmitted through it)
otransparent due to the highly-ordered arrangement of fibers (no blood
vessels/blood are present)
olots of nerve endings
-the aqueous humor, is a flued derived from blood, fills the space behind the cornea,
supply oxygen and nutrients to it
oaqueous humor: the water fluid in the anterior chamber of the eye
oremoves waste from cornea and lens
-to get to the lens, the light must pass through the pupil
opupil: the dark, circular opening at the center of the iris in the eye, where light
enters the eye
oiris controls the size of the pupil and how much light reaches the retina, via the
pupillary light reflex
oiris: consists a muscular diaphragm surrounding the pupil and regulates the light
entering the eye by expanding/contracting the pupil
-the light is currently at the vitreous chamber (space between lens and retina)
oit is refracted the fourth and final time by the vitreous humour
ovitreous humour: the transparent fluid that fills the vitreous chamber in the
posterior part of the eye
olongest part of the journey through the eyeball
o80% of the internal volume of the eye
oLike egg white consistency (YUM)
-Now the light is hopefully at the retina
find more resources at oneclass.com
find more resources at oneclass.com
oRetina: light-sensitive membrane in the back of the eye that contains rods and
cones. It receives an image from the lens and sends it to the brain through the
optic nerve
oONLY SOME OF THE LIGHT REACHES THE RETINA
Due to absorption and scattering
Light also gets lost in the eyeball, LOL wtf
The retina is where “Seeing” really begins #poeticAF
Focusing Light onto the Retina
-The optic components of the eye:
oemmetropia: there is no refractive error
the refractive power of the eye is
perfectly matched to the length of the
eyeball
avg. eyeball has +60 diopter (D)
a unit of measurement of the
optic power of a lens
omyopia: refractive errors occur when the
eyeball is too long relative to the power of the
optic components
nearsightedness
too long: image of the object will be
focused in front of the retina (seen as
a blur)
can be corrected with negative lenses
diverge rays of light before they enter
the eye
ohyperopia: refractive errors occur when the
eyeball is too short relative to the power of
the optic components
too short: image of the object will be focused behind the retina
farsightedness
increasing the power of the eyes, positive lenses
this converges the rays of light before they enter the eye
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Chapter 2: the first steps in vision: from light to neural signals. When determines how much the light must be bent by eyeglasses for it to be properly focused on the retina = refraction. Now the light is hopefully at the retina: retina: light-sensitive membrane in the back of the eye that contains rods and cones. It receives an image from the lens and sends it to the brain through the optic nerve: only some of the light reaches the retina. Light also gets lost in the eyeball, lol wtf. The retina is where seeing really begins #poeticaf. What this contraction does is reduces the tension on the zonules and enables the lens to bulge the fatter the lens is, the more power it has. Fat is power lmao lit!!!!: accommodation enables the power of the lens to vary by as much as 15 diopters.
