4.2 Vision I: The Eyes and the Brain Convert Light Waves to Neural Signals Flashcards
What is Visual Acuity?
Defined as the ability to see fine detail
Who designed the 20/20 vision measurement?
Hermann Snellen;
It is the smallest line of letters that a typical person can read from a distance of 20 feet.
What is Visible Light?
The portion of the electromagnetic spectrum that we can see, (which is an extremely small slice)!
What is the range, in nanometres which Visible Light falls under?
400-700nm
What are the shortest waves on the Visible Light spectrum?
Ultraviolet Rays
What are the longest waves on the Visible Light spectrum?
Infrared Waves
What does “wavelength” mean?
The distance between peaks of waves
What aspect of a wave determines the colour a human will see?
The LENGTH of a lightwave determines hue/color
What aspect of a wave determines the brightness a human will see?
The AMPLITUDE (height of the peaks) of a wave
What aspect of a wave determines the saturation or richness of colour a human will see?
The PURITY (number of distinct wavelengths that make up the light)
What’s the first part of the eye which light passes through?
The Cornea, which is a clear, smooth, outer tissue.
The Cornea bends the light coming in,
Where does the light go after it’s past the Cornea?
The Pupil, which is a hole in the coloured part of the eye
What are the three properties of light waves?
Purity
Wavelength
Amplitude
What is the name of the part of the eye which controls the size of the pupil? Why does it do this?
The Iris. By changing the size of the Pupil, the amount of light that can enter the eye changes
Retina
A layer of light-sensitive tissue lining the back of the eyeball
Define “Accomodation”:
The process whereby the eye maintains a clear image on the retina; the process by which infants revise their schemas in light of new information
What’s “Myopia”?
If the eyeball is too long, images are focused in front of the retina, leading to nearsightedness
You can see objects near to you clearly, but objects farther away are blurry
What’s “Hyperopia”?
If the eyeball is too short, images are focused behind the retina, and the result is farsightedness
You can see objects far away clearly, but objects up close are blurry
Two types of photoreceptor cells in the retina contain light-sensitive pigments that transduce light into neural impulses
What are the two types of photoreceptor cells in the retina, and what do they do?
Cones
Rods
They contain light-sensitive pigments that transduce light into neural impulses
These photoreceptor cells allow us to detect colour, operate under normal daylight conditions, and focus on fine detail
Cones
What do “Rods” do for our vision?
They become active under low-light conditions for night vision
What shades of colour do Rods produce?
None. They all contain the same pigment, which is perceived to us as shades of grey
Which photoreceptor is more sensitive?
Rods are more sensitive
However this comes at a cost, as they produce no information about colour
An area of the retina where vision is the clearest and there are no Rods at all
Fovea
