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Lecture 3

PSYC 211 Lecture Notes - Lecture 3: Opsin, Electromagnetic Spectrum, CyanPremium

3 pages49 viewsFall 2017

Department
Psychology
Course Code
PSYC 211
Professor
Gary Brouhard
Lecture
3

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Vision:
Photons act like a wave and a particle
Amount of energy is inversely proportional to the photon’s wavelength
Photons do all the wavelengths on the electromagnetic spectrum, but we’re
only gonna talk about the Visible Light part.
Photon in this section breaks the covalent bond in opsin which causes the
depolarization of the neuron (by use of a signal cascade)
Opsins are the proteins in our sensory receptors (NEURONS)
Four kinds: rod opsin (rhodopsin) and 3 cones (blue, green or red)
Each neuron only detects one wavelength of light because each neuron has
one opsin
Rod doesn’t interpret the colour/wavelength of light, just the amount of it.
The three colour sensors (cones) manage to convey all the colours of the
visual spectrum
Each cone has an optimal wavelength! Ex: green cone is 535nm, but it is 13%
activated at 610nm.
Each cone also has a different sensitivity to light (relative activity among the
three cones dictates the colour that the brain perceives)
A lot of modern TVs have 3 LED’s at each pixel (red green and blue), if
activated and at a far distance, look white!
Properties of light:
o Red + Green = yellow
o Red + blue = purple
o White: all colours are being reflected
o Light is additive, paint is subtractive
o Green light means you DON’T have red and blue (they have been
absorbed not reflected, otherwise you’d have white light
o When you paint, you are subtracting colours from the whiteness. Paint
doesn’t create light, just absorbs and reflects light.
o Magenta paint is just subtracting green (means you have red and blue
light)
o With paint, you try to subtract a single colour at a time so that it takes
lonegr to create black once you’ve subtracted all the colours
o Red paint: ALREADY SUBTRACTED TWO COLOURS and cyan! Cuz it’s
the combo of blue and green)
o Green, blue and red = used in TVs. Paint is magenta, yellow and cyan.
o Black = absence of light. 100% brightness = pure light
o Brightness = playing with just white and black
o Saturation (purity)= how much you deviate from center point in the
colour wheel (very close to white or very close to your colour)
Eye conditions:
o Protonopia: cone is defective because gene that makes protein is
defective (ex: red cones are filled with green cone opsin)
o Deuteronopia: green cones filled with red opsin
o Achromatopsia = see in black and white
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