What is light Newtons prism experiments Retinal motion signal Compa rator

# What is light newtons prism experiments retinal

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What is light? Retinal motion signal Compa rator Efferen ce copy Outflow Theory Eye movement signal from brain 47
o White light, passed through a prism, splits into a spectrum of different lights that appear coloured (refraction) o Repeat the process: no further decomposition occurs o Reverse the process: colours converge to form white again The prism does not destroy the character of light, it only reveals its components o A prism spreads the light out into its different components Electromagnetic spectrum: - The spectrum newton observed is only a small part of the broader electromagnetic spectrum - Wavelengths appear different in colour - Visible wavelengths range from 400-700nm (nanometres) - 1nm= 1m x 10 -9 – i.e a millionth of a mm - Many wavelengths are not visible to humans – above radio, tv – below gamma rays, x-rays Wavelength and colour: - What is wavelengths? o Light is (kind of) a wave o Wavelength is the distance between the crests (nm) - What is intensity? o Intensity is the height of the wave o Approximates to brightness - Different pure single wavelengths appear to us as different colours o Wavelength is an objective property of the stimulus Short wavelengths look pupleish/blueish Medium wavelengths look greenish Long wavelengths reddish o Colour is subjective property of the percept I.e. the experience you have when you see particular wavelength (or combination of wavelengths) It exists only in your head There are just wavelengths – we perceive these as colours Colour misconceptions: - ‘There are 7 colours: red, orange, yellow, green, blue, indigo and violet’ o Newton did divide the spectrum into 7 different named categories, but in reality the spectrum is a continuum o Any division into categories is to some extent arbitrary o Besides what able brown it is actually just dark yellow-orange i.e. lower intensity at approx. 600nm wavelengths - Objects seem to appear to omit light o Reflect light or absorb (subtract) it o Appear to be The colour of the light that they reflect Black if they absorb lots of light at all wavelengths and reflect little White if they absorb little light and reflects lots at all wavelengths Yellow if they absorb all other wavelengths and reflect only yellow (e.g. 580nm wavelength) - ‘White and black aren’t colours: they’re shades’ o Colour is an experience of a combination of wavelengths of light o Therefore, white and black qualify o The sum of all wavelengths or the sum of not many colours Additive colour mixtures: - We can add various pure wavelengths of light together to form an area that appears to be a new colour 48
- Although the combination of short and long wavelength (blue and red) light makes purple, the wavelengths of light have no changed - Light containing all wavelengths together appear white additive mixture of light - When you mix paints = brown this is because mixing paints is a subtractive process\ - Must add light not colours Subtractive colour mixtures: - Mixing paints is a subtractive process -