B1 Intermediate US 13375 Folder Collection
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Humans can discern between 2.3 million colours - but try staring at this picture of us bursting
through the periodic table and focus on the green dot as we invert the colours. Don’t
stop staring there until I say. The light is travelling as a wave to your eye, and the
frequency of these wavelengths determines the perceived colour of everything in this
picture and around you. Humans have trichromatic vision, meaning we have three cone cells in
our retinas, each which are sensative to different wavelengths of light: blue, green or red.
Keep looking at the green dot and your brain will do something pretty neat. Did the image
change back to the original colour? Even though you were staring at a black and white image,
your brain perceived it to be in colour.
This phenomenon is known as ‘after imaging’ - after staring long enough at the brightly
coloured image, your cones slowly become fatigued and the supply of photopigment in the respective
cones becomes exhausted, which ultimately stops sending signals to the brain. In the
case of this illusion, the part of the photo where you see cyan, the green and blue cones
become tired and as a result there is increased activity in the unfatigued red cones. So when
the image switched to black and white we see ‘red’ - cyan’s complementary colour.
Growing up, you likely learned about the primary colours red, yellow and blue - and their respective
complementary colours. But things are more complicated when you consider that the primary
colours in your printer are magenta, yellow and cyan, or that the screen you’re watching
this on uses red, green and blue! These are different colour models, where RGB is ‘additive’
meaning the mixing of different lights of colour create new colours - while the other
two are ‘subtractive’ models and absorb different wavelengths of light.
For example, when you hold a yellow object in real life (don’t use a lemon), it’s
actually absorbing every wavelength except yellow - that yellow light bounces back and
hits your eyes. But, when you look at this yellow object through your screen right now it’s actually
not yellow at all. Because your screen can only use red, green, and blue colours,
if you were to zoom in physically on anything yellow, it would actually be a combination
of red and green - and because the wavelength of yellow is between red and green, our brain
interprets this mix as yellow. (YELLOW SCREEN) So what you’re seeing here is in fact not
yellow at all, but it’s stimulating a mix of your red and green cones, which your brain
interprets as yellow.
While plants come in a range of colours, the predominant colour is green, due to chlorophyll,
the energy absorbing pigment found in plants critical for photosynthesis. So, to effectively
attract pollinators such as bees, insects and birds, flowers have evolved to stand out
against green. It’s why you don’t see many green flowers. And flowering plants have
even evolved a suite of different colours to attract specific pollinators - known as
pollinator syndrome. Bird-pollinated flowers are mostly red, potentially to discourage
visits from bees, as their visual system is different than birds, making it hard from
them to discriminate between red and green.
Similarly, we all have our own favourite colours, but why? One theory suggests that colour preference
is gendered, where given the choice between cyan and red, men prefer cyan colours and
women prefer redder colours. Researchers hypothesize this preference has evolved from our hunter-gatherer
societies where women's visual systems were specialized to see ripe red berries against
green foliage. Another theory suggest that we like hues that we associate with pleasant
things - however, pleasant and unpleasant things are often the same colour - we love blue slurpee
but not blue mold.
Investigating these questions of colour had us thinking about links between science and
art. So in our latest AsapTHOUGHT we asked both artists and scientists about how they
view their world.
Check it out with the link in the description
and subscribe for more weekly science videos.
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Will This Trick Your Brain? (Color TEST)

13375 Folder Collection
Sh, Gang (Aaron) published on August 17, 2016    Kuantse translated    Mandy Lin reviewed
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