# Physics: Color

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### The visible light occupies

a tiny part of the electromagnetic spectrum.

### When the frequency of light wave matches the natural vibrational frequency of atoms in a material, light wave is

either absorbed or scattered around
Resonance occurs and atoms start to vibrate with the large amplitude => they collide with each other a lot => they "waste" energy of the light wave => light wave dies out which means it's absorbed.

### Different colors of light correspond to different

frequencies of light waves emitted by an electron in an atom
and with a little knowledge of quantum mechanics you can understand that this frequency corresponds to the difference in energy values of an electron on two different orbits in an atom: the electron coming down from the higher to the lower orbit emits light of particular frequency.

red

### The color of an opaque object is the same as the color of the light that is

reflected by it
Opaque object doesn't pass the light through it. It absorbs part of incident light and reflects the other part. The frequency of the light wave reflected by the object will provide this object with the color (corresponding to the frequency of the reflected light wave: lowest frequency = red, highest frequency = violet).

### If sunlight were green instead of white, the most comfortable color to wear on a hot day would be

green
For green-colored opaque object reflects only... GREEN light! Therefore, if no other components rather than green is present in the sunlight, no light (and energy) will be absorbed, but rather reflected.

### The worst thing you can do for the health of a green-leafed plant is to illuminate it with only

green light.
for the green leaf will reflect 100 % of the incident light if this light contains green component only. Therefore, it will not absorb any energy, thus lacking energy for its growth.

### The color of a transparent object is the same as the light that is

transmitted
The object transparent for the light wave of particular frequency has a pigment in it that will absorb the light waves of all frequencies except for the light wave of this particular frequency that it will TRANSMIT through. The transmitted part of the light wave will provide this object with the color (corresponding to the frequency of the transmitted light wave).

blue

### A new red dress looks more expressive (red color is intensified) under

Incandescent lamp
red looks more intense when illuminated by incandescent lamp. Light from incandescent lamp has more intensity in the red part of visible light range, therefore intensifying red colors.

### The solar radiation spectrum is

a plot of brightness of sunlight versus its frequency.
Solar radiation spectrum shows how intensity (brightness) of different light waves comprising the sunlight DEPENDS on their frequency.

### The solar radiation spectrum has the highest intensity in... (Hint: of what color is the brightest light emitted by the sun?)

yellow-green part of the spectrum
It corresponds to the peak in light intensity in solar spectrum.

### Light of what color our vision is most sensitive to?

yellow-green
for this is the brightest region in sunlight spectrum.

### The primary additive colors are

red, blue, green.
These are the main colors of the solar radiation spectrum that can be ADDED together to obtain any other color!.

### The colored dots that make up the color on a TV screen are

red, blue and green

### If light beams of three primary colors shine on a wall they produce

a white spot
They all add to white color. Using color algebra: R + G + B = W.

### Complementary colors are two colors that

produce white light when added together.
that's why they are called complementary. Example: M + G = W.

### Magenta light is a mixture of

red and blue light

### A sheet of red paper will look black when illuminated with

cyan light.
Cyan light has no red in it (cyan and red are complementary colors, or cyan = green + blue). Therefore, no light wave is reflected if the incident light has no red component in it (red paper can reflect ONLY RED light).

### If sunlight were green instead of white, the most comfortable color to wear on a cold day would be

magenta
Magenta paint reflects light waves of all colors except for... GREEN! Why? Because magenta is complementary color to green (M + G = W), green light doesn't contain any magenta component in it: Therefore, it ABSORBS green, and if the sunlight is all green, magenta clothes do not reflect any light back, it absorbs 100 %.

### The yellow clothes of a stage performer can be made to look black if illuminated only by light that is

blue Blue and yellow are complementary colors, that means they do not reflect each other. Therefore, yellow clothes will not reflect blue light at all, so it will appear as having no color or BLACK.

subtraction

three plus black

### Look at a full-color picture in a magazine with a magnifying glass and you'll see that the inks used are

magenta, cyan, yellow, and black

### Which interacts more with sounds of relatively high frequencies?

The smaller the size, the smaller the wavlength of the wave this object can recognize.

### Which interacts more with light of relatively high frequencies?

small particles
Small particles interact with waves of the small wavelength (waves of high frequency)!

### The sky is blue because air molecules in the sky act as tiny

resonators (tuning forks) which scatter blue light.
Molecules have the size comparable to the wavelength of violet and blue light waves, therefore these molecules will interact with light of blue and violet color the most. So they will scatter this light the most and the sky will appear blue (eyes are not very sensitive to violet color).

### Sunsets are red, because

only the light wave of the long wavelength (that of the red color) "survives" scattering.

### The sun appears red at sunset as a result of the

longer path of air through which sunlight travels before reaching our eyes.

### If we lived on a planet where red light was most scattered in the atmosphere and the blue light was least scattered in the atmosphere, the sky would look

red and the sunsets blue.

### The whiteness of clouds is evidence of a variety of

sizes of the cloud molecules.
Light waves of all wavelengths (from violet to red) are scattered on all these different particles making the cloud to have all colors at once, which means white color.

### The greenish blue (cyan) color of sea water is evidence for the

absorption of the light of red color
Cyan is the complementary color for red, therefore, if red light is absorbed and other light is reflected, the reflected light will have the color complementary to the red: that of the cyan. Color algebra: W - R = G + B.

### A flag that is red, green, and white is viewed deep beneath the ocean surface via reduced intensity sunlight at that depth. The red, green, and white would likely appear

black, green, and cyan.
for the red part of the flag would have no red component in the sun rays' light to reflect, green would barely make it, and the white part minus red would be cyan.

infrared

### The fact that you can get sunburned while submerged in water is evidence that water

transmits ultraviolet light

### The fact that you can get sunburned while in the shade is evidence that the air molecules of the atmosphere

scatter ultraviolet light.

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