Physics Ch. 28 Color

The color of an object we see is determined by the

1) colors of light reflected by the object. 2) frequencies of light absorbed by the object. 3) colors of light shining on the object. 4) frequencies of light reflected by the object.

Sunsets are red because

1) the longest path of sunlight through the atmosphere is at sunset or sunrise. 2) a lot of high-frequency light is scattered by the atmosphere. 3) blue light from the sun is scattered by Earth's atmosphere.

What is a line spectrum? How is it observed? What is it used for?

A line spectrum is the result of passing a light beam containing many different colors through a prism or a diffraction grating. Each color of light will refract or diffract at a different angle, making it possible to observe the individual colors of light making up the ray. These can be seen with the naked eye through the eyepiece of a spectroscope, or recorded on photographic film in a spectrometer. The line spectrum can be used to identify atomic constituents of matter.

A photograph of your favorite person's yellow sweater shows as what color on the negative?

Blue

What is color subtraction? When do we use it? What color do you get when you mix blue paint with yellow paint? Explain.

Color subtraction occurs when we mix paints. Each paint or pigment reflects certain colors of light and absorbs the others. The colors reflected by a mixture of pigments are those that are not absorbed. This process is called color subtraction. When you mix blue paint with yellow paint the only color that both pigments reflect is green. All other colors incident upon the mixture are absorbed; therefore the result is green paint.

Some electrons in atoms vibrate at a characteristic frequency that produces white light.

FALSE

The sky is blue because air molecules absorb blue light.

FALSE

Two colors of light that add together to form black light are called complementary colors.

FALSE

A spectroscope is an instrument that analyzes the colors in a light beam.

TRUE

If an object were completely black, you wouldn't be able to see it directly.

TRUE

Material in an object that selectively absorbs colored light is called a pigment.

TRUE

Tennis balls are yellow-green because our eyes are most sensitive to that color.

TRUE

Explain why the sky is blue.

The sky is blue because nitrogen and oxygen molecules scatter the higher frequencies of light much more than they scatter the lower frequencies of light. Therefore, violet and blue light are scattered the most by atmospheric molecules. Although violet light is scattered more than blue light, our eyes are much more sensitive to blue light, so we see a blue sky.

What are the three primary colors for light addition? What colors appear when lights of any two primary colors are shone on a white object? How would you guess a TV set makes purple?

The three primary colors of light for additive color mixing are red, green, and blue. When any two primary-color lights shine on a white object, the object appears to be the complementary color of the third primary color. For example, red and green light add to yellow, which is the complementary color of blue. A TV set makes purple by using red and blue light.

What is the true color of water? Explain.

Water is greenish blue. This is because water molecules absorb infrared light and small amounts of red light. When any color is subtracted from incident white light, it is the complementary color that remains. The complementary color of red is cyan (greenish blue); hence, water looks greenish blue.

When a sample of an element is heated until it glows, the color it gives off is

a composite of many frequencies of light.

The reason the sky is blue is that air molecules

absorb and then reemit blue light, scattering it in all directions

Colors seen on TV result from color

addition.

When blue and yellow paints are mixed together, the result is green. The reason for this is that

between blue and yellow pigments, all colors are absorbed except green.

If molecules in the sky scattered orange light instead of blue light, sunsets would be colored

blue.

The white caps of waves as they overturn are evidence that the water has

broken into an assortment of tiny particles that scatter all colors.

A sheet of red paper will look black when illuminated with

cyan light.

The complementary color of green is

cyan.

Different colors of light correspond to different light

frequencies.

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

green.

The true color of water is

greenish blue.

The colors of light emitted by incandescent gases show the

identities of atoms in the gas.

The three paint colors that are useful for color subtraction are

magenta, cyan, and yellow.

When red and blue light shine on a white sheet, the resulting color is

magenta.

Clouds are white because water molecules

of different sizes form clusters, scattering different colors of light.

Complementary colors are two colors that

produce white light when added together.

Magenta light is really a mixture of

red and blue light.

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

red, blue, and green.

If the atmosphere were 50 times thicker than it now is, the sun would appear

red-orange.

The cyan color of ocean water is evidence that the water absorbs

red.

The color of an opaque object is determined by the light that is

reflected.

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

resonators that scatter blue light.

Spectral lines in a line spectrum take the shape of lines because the

slit of the spectroscope is itself a line opening.

If you're looking for an instrument that tells what stars are made of, look for a

spectroscope.

Colors seen on a photograph result from color

subtraction.

Light shines on a pane of green glass and a pane of clear glass. The temperature will be higher in

the green glass.

A tennis ball is most easily seen if its color is

yellow-green.

Humans are most sensitive to light that is

yellow-green.

Sunlight contains all colors of light, but much of it is

yellow.

When red and green light shine on a white sheet, the resulting color is

yellow.

the complementary color of blue is

yellow.