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From the spectrum lab: Light waves with different wavelengths appear as different colors. Short waves are blue/purple. Long waves are red.

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Presentation on theme: "From the spectrum lab: Light waves with different wavelengths appear as different colors. Short waves are blue/purple. Long waves are red."— Presentation transcript:

1 From the spectrum lab: Light waves with different wavelengths appear as different colors. Short waves are blue/purple. Long waves are red.

2 Missing colors? Can you find these colors in the spectrum?

3 More than just wavelength... There is no “brown” or “pink” wavelength of light. Color is a PERCEPTION, not a reality. That is: – Color only exists in your mind.

4 False motion

5 Scintillating Blocks

6 Shadow and Color

7 White’s Illusion

8 Opponent Afterimage

9 McCollough Effect

10 Color opponency

11 What is going on? You cannot trust your brain. Your perception of the world is different than the actual world.

12 Other color craziness [Greenpro2009 videos: chameleon, color constancy] [Himba Tribe study]

13 Real spectra... Objects emit/reflect light with different sets of wavelengths. – Bright in areas, dark in others:

14 Perfect emitter at 4000 K:

15 The Sun:

16 Electrified neon gas

17 Spectra and the eye Eyes can’t see all that detail. Can’t measure the amount of light of every wavelength. They check THREE PARTS of the spectrum... – red, green, and blue parts

18 Rods and Cones Four types of light-detecting cell in your eye: – Rods: very sensitive to all light – Cones: less sensitive, tuned to certain colors (Red, Green, Blue)

19 Rods and Cones Sensitivity of the 3 cone cells:

20 Primary colors 3 cones → 3 primary colors Computers and TVs display colors with an “RGB” system for Red, Green, and Blue.

21 RGB Pixels

22 Color Addition

23 Primary colors “Red, yellow, blue” are a BAD CHOICE for primary colors. Even in pigments! They can’t make a full color gamut (range). Cyan, Magenta, and Yellow form the CMYK system for pigment/ink.

24 Color Subtraction

25 Different numbers of cones Some humans only have 2 types of cone! They are color deficient or color blind. (About 1% of men.) Some women may have 4 cones!! They’d see differences in color that nobody else does! Tetrachromacy in humans is a new, uncertain discovery.

26 Colorblindness test

27 Colorblind simulation: red-green def. blue-yellow def.

28 Cones in other animals Most mammals have 2 types. – Dogs don’t see in black & white! – It’s just a limited set of colors. Higher primates have 3 types. Some birds, reptiles, and insects have 4 or even 5!

29 Different cone sensitivity The cone cells in most birds and insects can detect ultraviolet! Many things have “hidden” features that they can see!


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