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