The light sense Flashcards
what is the change in sensitivity described as
for cones it is described as V λ(vee lambda) curve and for rods its V’λ(vee prime lambda)
why does the sensitivity of the eye vary
it varies according to wavelength of light and overall luminance level because of differences in rod and cone sensitivity
what is transduction
first step on the conversion of light energy into visible perception(when light reaches rods and cones)
what limits the amount of light reaching the photoreceptors
some light is lost through reflection at optical interfaces, the pupil also limits light, also the optical density of the media and spectral absorption of intervening tissue
what does the intensity of reflection depend on
the refractive indices of media through which light passes
what does the pupil do
It acts as the lights entrance to the eye- the smaller the pupil the less light getting through and the less retinal illuminance
what is the relationship between transmission and optical density
transmission is inversely related to the optical density of a medium so t=10^-d
what protects the retina from spectral absorption
the most protection of the retina comes from the lens but the cornea also absorbs short wavelengths
what wavelength does the crystalline lens absorb strongly
It absorbs short wavelengths so blue light
what is the purpose of the lens
to focus light and prevent harmful radiation from reaching retina
what light gets scattered more in the lens
blue light gets scattered 16 times more than red
where does pre retinal absorption occur
in the crystalline lens
where does retinal spectral absorption occur
in the macula
what is the macular lutea
central retinal region containing non photosensitive yellow pigment
what is the yellow pigment comprised of
it comprises two carotenoid pigments- lutein and zeaxanthin which absorbs some light
