week 2: vision Flashcards
for an object to be visible it must:
emit or reflect light
what is light
one part of a continuum called electromagnetic radiation (EMR)
when is an emr generated
when an atom emits a particle called photon
what determines the emr wavelength
the energy of the wave length
how much light does the human eye detect
only able to detect light within a narrow range of wavelengths
what gives rise to the perception of different colours
different wavelengths within the range of visible wavelengths
what is saccades
the constant movement of the eyes
what happens if an image stays stabilised on the retina
it disappears as the photoreceptors stop firing and the brain fills in the missing information
what are ciliary muscles
muscles in the eye that control the shape of the lens to accomodate near or far targets
if the ciliary muscle relaxes what happens
the lens bulges and therefore focuses on the far and blurs the near
if the lens is round what is the focal point
the far is blurred and the near is focused
what does it mean to be far or short sighted
the focal point doesnt land right at the retina where it is meant to land
at what age does your eyes stop focusing
40
why do we have 2 eyes
so we have a back up and to derive more information from the image/environment
what is stereovision good for
depth perception
what is motion paralex
the more an object moves when you move your head the closer the object is to you
what part of the eye contains the most photoreceptors
the fovea
types of photoreceptors
cones and rods
what are cones good for
colour and detail
when is cones most active
during daytime/in good light
why are photoreceptors facing away from the light is travelling
Human vision was designed for use in poor lighting (scotopic/night vision). Therefore photoreceptors are extremely sensitive to light that light is toxic to photorecptors.
what kills photorecepetors
too much light causes the photoreceptors to oversaturate and remove colour which bleaches the photoreceptors and causes them to be inaffective
How does the choroid layer work to protect photoreceptors
the choroid layer absorbs most of the light and reflects a small amount of light back to the photoreceptors
where are cones located
fovea and periphery
how many cone cells are there
6 million
what are rod cells
low detail and low light, good for scotopic/ night time vision
where are rods located
periphery
how many rods are there
120 mil