Light And The Eye (3) Flashcards
How is electromagnetic energy usually described?
In terms of wavelength - the distance between the peaks of the electromagnetic waves
What is wavelength distance measured in for visible light (as opposed to normal metres)
Nanometres
What does the visible spectrum for humans range from?
400-700nm (because X-rays and UV are harmful for our DNA - too low nm)
Cornea
The transparent tissue at the very front of the eye
Sclera
Tough white tissue that coats the rest of the eye (white part of eye)
Iris
Muscle tissue that controls the size of the pupil and therefore the amount of light that enters the eye
Accomodation*
When the ciliary muscles are tightened which causes the lens to thicken and focus on the objects that are closer to you
Common optical problem: MYOPIA**
Inability to see distant objects clearly
Image is focused on retina when lens is ‘RELAXED’
Refractive myopia - cornea or lens bends too much light
Axial myopia - eyeball is too long
Common optical (problem?) PRESBYOPIA*
The near point is the distance where the lens can no longer adjust to close objects
(Distance of this increases with age)
Common optical problem: hyperopia or far sightendness*
Inability to see nearby objects clearly
Focus point is behind the retina
(Usually caused by an eyeball that is too short)
Which part of photoreceptors contain the light-sensitive visual pigment**
The outer segments
Light is transduced into electricity here
Which 2 components do the visual pigment molecules in photoreceptors consist of **
OPSIN - a large protein
RETINAL - a light sensitive molecule
Isomerisation
(Visual transuction occurs) retinal (light-sensitive molecule) changes its shape and absorbs light
Why don’t we see the blind spot
One eye covers the blind spot of the other (the brain ‘fills in’ the spot)
Which are more sensitive to light - rods/cones?
Rods (rods take less light to respond)
But rod pathways to the brain cannot resolve detail as well as cone pathways
