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Chapter 4.2

PSYA01H3 Chapter 4.2: PSYA01H3 Chapter 4.: PSYA01_Ch4-2

Course Code
Steve Joordens

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4.2 The Visual System
- How the Eye gathers Light
o Light refers to radiation that occupies a relatively narrow band of the
electromagnetic spectrum
travels in waves and vary in length and amplitude
o Wavelength is the distance between peaks of a wave
long wavelengths are reddish
short correspond with bluish colours
o Amplitude (or height) of the peaks of waves
gives different experiences
Low-amp waves correspond to dim colours
High-amp waves correspond with bright colours
o we do not see pure colouration, rather, what we see is based on a mixture of
wavelengths that vary by hue (on the spectrum), intensity (brightness) and
saturation (colourfulness/density)
- Structure of the Eye
o Sclera is the white outer surface of eye
o Cornea is the clear layer that covers the front of the eye
contributes to eye’s ability to focus
o Pupil regulates the amount of light that enters by changing its size
it dilates to allow more light to enter
constricts to allow less light into eye
o Iris is a round muscle that adjusts the size of the pupil
gives eyes their colour characteristic
o Lens is behind the pupil
a clear structure that focuses light into back of eye
o rear portion of the eye consists of a layer of specialized receptors that convert
light into a message that the brain can interpret
- The Retina: From Light to Nerve Impulse
o Retina lines the inner surface of the eye and consists of specialized receptors
that absorb light and send signals related to the properties of light to the brain
o Optic Nerve is a dense bundle of fibres that connect to the brain
o Cones are the photoreceptors that are sensitive to the different wavelengths of
light that we perceive colour
o Fovea is the central region of the retina that contains the highest concentration
of cones
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