Vision: Physiology Flashcards
If light rays are absorbed, not reflected, by an object, what do we see?
Dark object
If light rays of many wavelengths are reflected off an object, what do we see?
White object
If red light rays are absorbed, but blue one are reflected, what do we see?
Blue object
What is LIGHT?
Packets of energy travelling in wavelike fashion at high speed (300,000 km/s)
How fast does LIGHT travel through less dense materials?
Very fast
How fast does LIGHT travel through dense material?
Slowly
How fast does LIGHT travel through more dense materials?
Slower
What does “refraction” mean?
LIGHT is bending
How does the density of an object affect refraction?
The more dense, the more it refracts
How will LIGHT RAYS from a distant object arrive at your eye?
They will arrive in parallel lines (see notes for a pic)
How will LIGHT RAYS from a close object arrive at your eye?
They will diverge (see notes for a pic)
Where does 75% of REFRACTION occur?
In the CORNEA
Why does most REFRACTION occur at the CORNEA?
Because the biggest difference in density occurs between air (1.00) and the CORNEA (1.38), and more density = more REFRACTION
Where does 25% of REFRACTION occur?
At the LENS
Why is there less REFRACTION at the LENS than there is at the CORNEA?
Because the difference in density between the AQUEOUS HUMOR (1.33) and the LENS(1.40) is much smaller than the difference of density between air and the CORNEA
Can the REFRACTIVE power of the CORNEA ever change?
No, because the shape of the CORNEA is unchanging
Can the REFRACTIVE power of the LENS ever change?
Yes, because the LENS can change shape
When is the REFRACTIVE power of the LENS decreased?
When the LENS is flat
When is the REFRACTIVE power of the LENS increased?
When the LENS is round
Are our eyes preset for close-up vision?
No, they are preset for distant vision
What is happening to structures inside the eye when focusing on a distant object?
CORNEA = unchanging (refracts LIGHT) LENS = flat (refracts LIGHT) NEURONS = sympathetic CILIARY MUSCLES = relaxed, dilated CILIARY ZONULE = pulled taut
What is BINOCULAR VISION?
Parallel RAYS can land on FOVEA when eyes face forwards
Why do PUPILS dilate when focusing on a distant object?
To allow more parallel LIGHT RAYS in
What stimulates the PUPILLARY DILATOR MUSCLES to allow more LIGHT in?
The sympathetic system
