Physics (Color)
The eye responds to 3 cones of light-- what are they?
(Blue) Cone 1: Short wavelength, resonates 400nm -> 525 nm Peak: 445nm (indigo) (Green) Cone 2: Medium wavelength, resonates 450nm -> 650 nm Peak: 535nm (green) (Red) Cone 3: Long wavelength, resonates 500nm -> 700 nm Peak: 575nm (yellow-green)
Define: Complementary Colors
Any two colors of light that, when mixed together in equal intensities, produce white.
When is light reemitted?
At frequencies below or above resonant frequencies, light is reemitted. If the material is transparent, the reemitted light passes through it. If the material is opaque, the light passes back into the medium from which it came (this is reflection).
A red filter has pigment that resonates at the frequency of ______ light. A) All of these B) Cyan C) Yellow D) Red
B) Cyan
A green object under yellow light and red film appears?
Black (refer to diagram in notes)
Yellow light shines on a blue object. What color does the object appear as?
Black (reflects blue, absorbs yellow)
A blue object under magenta light appears _________?
Blue
Cyan + Magenta =
Blue
Define: color mixing (by addition)
Color mixing by addition is the mixing of light of different frequencies
Define: color mixing (by subtraction)
Color mixing by subtraction is the mixing of colored paints or dyes, which absorb most frequencies except for the ones that give them their characteristic color
Define: Non-Spectral color
Consists of more than one wavelength *Non-Spectral only: - Brown - Grey - Pink - Magenta (R+Blue) - Purple (R + V)
Define: Spectral color
Consists of only one wavelength *Spectral only: - Red - Violet
Blue + Green =
Cyan
What color is water?
Cyan *If you are approximately 30m deep in water wearing "red," it will appear black
What are the 3 pigment colors?
Cyan, Magenta, Yellow
What are the 3 subtractive primary colors?
Cyan, Magenta, Yellow
Cyan ink pigment contains particles which resonate with relatively ________ frequency light. A) High B) All C) Medium D) Low
D) Low
True/False: A "magenta" shirt appears orange under red light
False
True/False: An emission spectrum for a given substance could be composed of lines of the following colors: magenta, brown, orange, and red.
False
True/False: If the atmosphere above the earth was to shrink in depth so that there were fewer particles to scatter sunlight, then the sun would appear yellower during the day.
False
True/False: Your bathroom is lighted by two lightbulbs, one green and one red, so when you observe your red shirt in the mirror, it appears yellow.
False
True/False: Black is a color
False. Black is not a color, but the absence of light. Objects appear black when they absorb light of all visible frequencies.
True/False: Black objects absorb all light that falls on them
False. Black objects that we see do not absorb all light that falls on them (there is always some reflection on the surface or else we wouldn't be able to see it). Ex: Carbon soot
True/False: White is a color
False. White is not a color, but a combination of all colors. Ex: "White light" is sunlight
An object under sunlight looks magenta. What color is absorbed?
Green
Yellow + Cyan =
Green
When is light absorbed?
Light is absorbed when its frequency matches a natural vibration frequency of electrons in the material illuminated by the light.
Red + Blue =
Magenta
What are the 4 printing pigments?
Magenta, Cyan, Yellow, and Black *Mixing these pigments produce a variety of hues
Green filter absorbs ________ and transmits _________?
Magenta, Green
Lowest -> Highest frequency in colors
ROYGBIV (400-700 Hz)
A cyan dress would absorb what color?
Red
Yellow + Magenta =
Red
Yellow and blue light shine on a red object. What color does the object appear as?
Red
Yellow light shines on a red object. What color does the object appear as?
Red (absorbs yellow, reflects red)
What are the 3 pairs of complementary colors?
Red and Cyan Green and Magenta Blue and Yellow
What are the only 3 colors that, when combined, produce white?
Red, Blue, and Green
What are the 3 additive primary colors?
Red, Green, Blue *The eye sees a combination of red, green, and blue light of equal brightness as white
Define: Spectrum
Spread of colors: ROYGBIV
Define: Pigment
The material in glass that selectively absorbs colored light. Electrons in the pigment atoms selectively absorb light of certain frequencies in the illuminating light. Ex: a red pigment absorbs cyan light / a yellow pigment absorbs blue light / a blue pigment absorbs green and red light
What gives the sky its blue color?
The scattering of violet and blue frequencies of sunlight in all directions. Our eyes are more sensitive to blue, so we see a blue sky.
Define: Emission Spectra
The spectrum of electromagnetic radiation emitted from a source. A substance is given electrical energy: the electrons jump to a higher energy level and when they return to lower energy level, they emit the "extra" energy as ONE wavelength
True/False: If we view the sun from above the atmosphere, it is pure white. However, because of our atmosphere, it appears with a hint of yellow.
True
True/False: The color of an object is due to the color of the light it reflects (if opaque) or transmits (if transparent)
True
True/False: Under a yellow spotlight in a theater, a rubber ball appears yellow, so it is possible that in sunlight it appears white.
True
True/False: color is a psychological sensation
True
True/False: glass absorbs ultraviolet light
True
True/False: Pigment can only reflect/absorb wavelengths that strike it
True Ex: Sunlight can absorb all wavelengths, candlelight can absorb ROYG, incandescent lightbulbs can absorb ROYgbiv, fluorescent lightbulbs can absorb royGBIV
True/False: An object can reflect only light of frequencies present in the illuminating light
True. The appearance of a colored object therefore depends on the kind of light used. Ex: shining a red light on a red rose makes the rose warmer (b/c rose will absorb rather than reflect light); however, shining a green light on a red rose makes the rose appear black (b/c there's no red to reflect)
Define the effect of white light
Under white light, white objects appear white and colored objects appear in their individual colors
Shortest -> Longest wavelength in colors
VIBGYOR (400-700 nm)
Why is the sunset red?
When sunlight travels a long path through the atmosphere (as at dawn or sunset), only the lower frequencies of light are transmitted and the higher ones are scattered out.
Green + Magenta =
White
Red + Cyan =
White
Yellow + Blue =
White
Blue is reflected. What color is absorbed?
Yellow
Red + Green =
Yellow
Yellow filter transmits what?
Yellow
What are all of the Spectral/Non-Spectral colors?
Yellow Cyan Orange Green