Physics Chapter 22

Your brain perceives color by an additive process. How would you see (a) red + blue; (b) blue + green; (c) red + green ;and (d) red + blue + green?

(a) magenta, (b) cyan, (c) yellow, (d) white

At 1 meter from a light source, a 1 m squared area has a light intensity of 0.8 W/m squared. At 3 meters from a light source, a 1 m squared area will have a light intensity that is _____ W/m squared.

0.09

If the intensity of light at 1 meter from a source is 1 w/m squared, it will be _____ w/m squared at 2 meters from the source.

0.25

If 16 seconds passes between seeing a lightning strike and hearing thunder, about how far away was the lightning?

3.36 miles

In terms of the absorption and reflection of light, describe the difference between a black piece of cloth and a white piece of cloth.

A black piece of cloth will absorb all colors of the visible light spectrum. This means that very little or no light is reflecting to your eyes off of the surface. In contrast, a white piece of cloth reflects all colors of visible light. The mixture of all colors of visible light is white light.

Why do we see lightning before we hear thunder?

Because light travels faster than sound.

Why is mixing pigments called color subtraction?

Because pigments absorb all the colors you don't see and reflects only the one that you do see.

If a cloth appears in white light is viewed in a room filled with only blue light, what color will appear?

Blue

What color of visible light has the most energy?

Blue

Another name for the subtractive color process is the ______ ________.

CMYK process

Which photoreceptors in your eye respond the least in dim evening light?

Cones

_______ are photoreceptors that respond to color.

Cones

If you wanted to make green paint, what combination of pigments would you use?

Cyan and yellow

What are the three subtractive primary colors?

Cyan, magenta, and yellow

True or False: A white object absorbs red light.

False, it reflects red light

___________ light bulbs produce light by passing electricity through a gas.

Fluorescent

How is an incandescent bulb different from a fluorescent bulb?

Fluorescent generate light but little heat, are more efficient than incandescent, incandescent bulbs generate light and a lot of heat.

In the CMYK color process, why is black pigment used instead of mixing cyan, magenta, and yellow pigments?

Impurities in the pigments result in a muddy gray color when cyan, magenta, and yellow are mixed. A purer black color can be obtained when black pigment is used. In addition, ink is expensive, so mixing three separate ink colors would use three times the ink as printing with black ink.

__________ light bulbs produce light by heating a metal filament.

Incandescent

Arrange the following in order of speed from fastest to slowest: sound waves, light waves, water waves.

Light waves, sound waves, water waves

How would you create the following colors using inks on paper: red, green, blue, white?

Magenta and yellow; yellow and cyan; magenta and cyan; no pigments

If a store clerk adds more colorants (pigment) to a can of white paint, what happens to the light we use to view the paint?

More colors are subtracted from the light and absorbed by the paint.

__________ in the back of the eye absorb light and create a sense of vision.

Photoreceptors

Another name for the additive color process is the ____ ______ ______.

RGB color process

Identify the color process (RGB or CMYK) used in each step. (a) Taking a photograph with a digital camera. (b) Transferring the image to a computer. The image appears on a computer monitor. (c) Printing the image using a laser printer. (d) Seeing the image on the paper with your eyes.

RGB, RGB, CMYK, RGB

What color of visible light has the least energy?

Red

What colors of light are reflected by the color magenta?

Red and blue

What are the three additive primary colors?

Red, green, and blue

What is the difference between reflection and refraction of light?

Reflection is the bouncing of light off a surface, and refraction is the bending of light as it moves from one material to another.

____ are photoreceptors that respond to black, white, and shades of gray.

Rods

Which photoreceptors in your eye respond the most in dim evening light?

Rods because they are more sensitive

An image of a sunset is displayed on a computer screen. This image is then printed onto a piece of paper by a printer. When the paper is held up next to the screen, the images are almost identical. What is the difference between the processes used to create these two images?

Since the computer monitor makes its own light, the image on the screen is created with the RGB color process and uses red, green, and blue light in different combinations to make all the colors in the image. This is the additive color process. The image on the paper is created using the CMYK color process and uses cyan, magenta, yellow, and black colored inks in different combinations to make all the colors in the image. This is the subtractive color process.

What determines the color of an object?

The composition of the light on the object, how the object reflects light, how the object absorbs light, and the material of the object

You are reading a book by the light of a lamp. Compare the intensity of the light on your book at 1 meter away from the lamp to the intensity of the light on your book at 4 meters away from the lamp.

The light 4 meters away will be 1/16 the intensity of the light 1 meter away.

How does a color printing press produce all the colors of a printed picture?

The printing press uses the CYMYK process (subtractive color process), mixing cyan, magenta, yellow, and black pigments to produce the colors of the picture.

Which star would be hotter, a star that produces blue light or a star that produces red light?

The star with blue light

How does a color television screen produce all the colors you see on the screen?

The television screen uses the RGB process (additive color process), mixing red, blue, and green dots of light (or pixels) to produce the light seen on the screen.

Describe the role of atoms in producing light in a fluorescent light bulb.

To make light, fluorescent bulbs use high-voltage electricity to excite atoms of gas that fill the bulb. The atoms of gas, as a result, release ultraviolet light that we cannot see. However, the ultraviolet light excites the atoms (of phosphorus) in the white coating of the bulb. The atoms in the coating then emit visible light.

True or False: A blue object absorbs red and yellow light.

True

True or False: A green object reflects green light.

True

True or False: A yellow object reflects red light.

True

________ _____ is made up of all the possible colors of light.

White light

What is white light in terms of other colors?

White light is the combination of all colors.

For stage lighting for a play in a theater, a magenta spot of light is created and a green spot of light. What happens when these two spots of light combine?

You get white light.

Which of the following is not a quality of light: intensity, color, high speed, acceleration?

acceleration

The three ________ _______ ______ are red, green, and blue.

additive primary colors

Creating color by changing the strengths of signals of three primary colors is a(n) _________ ______ used by TVs.

additive process

A prism separates light into different wavelengths of ______.

color

The power of light per unit area is light ________.

intensity

Light intensity is measured in units of _____ per ________.

power/watts, meters squared

The three ________ ______ ______ are cyan, yellow, and magenta.

subtractive primary colors

Creating color by relying on the reflected and absorbed light of three primary colors is a(n) __________ _______ used to dye fabric.

subtractive process