Additive and Subtractive Colors, Study notes of Physics

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KACY Bassitt - Additive and Subtractive Colors

Physics (Winston Churchill High school)

KACY Bassitt - Additive and Subtractive Colors

Physics (Winston Churchill High school)

Name: Kacy Basitt Date: 03/02/

Student Exploration: Additive Colors

Directions: Follow the instructions to go through the simulation. Respond to the questions and prompts in the orange boxes.

Vocabulary: additive color, cyan, magenta, primary colors, RGB value, secondary color, visible spectrum

Prior Knowledge Questions (Do these BEFORE using the Gizmo.) When white light passes through a prism, it splits into a rainbow of colors. These colors make up the visible spectrum shown below.

1. What is the order of colors in the visible spectrum?

red, orange, yellow, green, purple, blue

2. What do you think would happen if all of the colors of light in the visible spectrum were

blended together? if blended it would probably turn black

Gizmo Warm-up On a computer or TV screen, all the colors you see are mixtures of only three primary colors of light. In the Additive Colors Gizmo, you will explore how the primary colors can be mixed to make any color.

1. The primary colors are listed on the left side of the Gizmo.

What are they? red, green, blue

2. Check each box to turn each color on. Notice that the intensity of each color can be adjusted with the slider. What happens to the color if you move the slider to the left?

moved to the left the color becomes darker then fades away.

3. Turn on Show RGB values at the mouse location , and move each slider to the right. The RGB value gives how much red, green, and blue light is in a given color. Move the cursor over each colored circle. List the RGB values of each pure color below.

Red: 250 0 0 Green: 0 250 0 Blue: 0 0 250

Activity B:

Creating colors

Get the Gizmo ready: ● Move the red, green, and blue circles so they completely overlap. ● Check that the Red , Green , and Blue values are all set to 255.

Question: How can any color be made from a combination of red, blue, and green light?

1. Predict: How do you think you could use the Gizmo to make the color gray?

By overlapping the colors

2. Observe: Change the Red , Green , and Blue values to 90. What color does this produce?

the color is a dark gray

3. Create: Using the Gizmo, try to create a color that matches each description below. Write the RGB value of each color that you create. In the last row of the table, describe your own object or color and give its RGB value.

Description RGB value A pale blue sky 145,255, A brown dog 100,70, A delicate pink rose 255,200, An orange pumpkin 255,140, A royal purple robe 195,120, 255,240,

4. Calculate: Describe the RGB value and color you would obtain with each combination described below. Use Gizmo to check your answers. RGB Value Color

A. Yellow (255, 255, 0) and blue (0, 0, 255) 255,255,255 white

B. Plum (120, 0, 120) and dark green (0, 120, 0)

C. Teal (0, 90, 90) and bronze (185, 150, 0)

5. Summarize: If you know the RGB values of two colors of light, how could you calculate the RGB value of a mixture of the two colors?

I think that you could could calculate the RGB values by adding together

Name: Kacy Bassitt Date: 03/02/

Student Exploration: Subtractive Colors

Directions: Follow the instructions to go through the simulation. Respond to the questions and prompts in the orange boxes.

[NOTE TO TEACHERS AND STUDENTS: This lesson was designed as a follow-up to the Additive Colors Gizmo. We recommend you complete that activity before this one.]

Vocabulary: absorb, CMY value, complementary color, cyan, magenta, primary colors, reflect, RGB value, secondary color, subtractive color, transmit

Prior Knowledge Questions (Do these BEFORE using the Gizmo.) A color printer can print any color by mixing three primary colors of ink: cyan (light blue), magenta (bright pink), and yellow.

1. What color do you think you would get if you mixed cyan and magenta? dark purple
2. What color do you think you would get if you mixed cyan and yellow? like a green
3. What color do you think you would get if you mixed magenta and yellow? like a dark orange

Gizmo Warm-up We see objects when light from that object enters our eyes. Some objects produce their own light, while others transmit or reflect light. The Subtractive Colors Gizmo allows you to explore how light is absorbed and reflected by colored pigments such as paint.

Three primary colors of light—red, green, and blue—combine to make white light. Turn on Show RGB values at the mouse location to see how much red, green, and blue is in each color.

1. Move the cursor over a white area. What is the RGB value of white? 255,255,
2. Move the cursor over the cyan circle. What is the RGB value of cyan? 0,255,
3. Assume the cyan circle is a painted spot that is illuminated by white light. Some of the white light is absorbed by the cyan pigment, and some is reflected into your eyes. A. What colors of light are reflected by the cyan spot? green

B. What color of light is absorbed by the cyan spot? red

Activity B:

Creating colors

Get the Gizmo ready: ● Check that the Cyan , Magenta , and Yellow values are 255. ● Check that Show RGB values is on.

Introduction: When more light is added to a mixture, the resulting color becomes lighter. When more pigment is added to a mix, the resulting color becomes darker. For this reason, colors formed by mixtures of pigment are called subtractive colors.

Question: How is the RGB value of a pigment mixture determined?

1. Observe: Overlap the magenta and yellow circles to make a circle of red. Then move the cyan circle over the red circle. What is the result of combining red and cyan pigment?

black pigment

2. Investigate: Because they combine to make black, red and cyan are called complementary colors. Use the Gizmo to determine the complementary colors of magenta and yellow.

The magenta and yellow colors make a red color.

3. Gather data: Move the three circles so they completely overlap each other. Use the sliders to create each of the described colors in the table below. Record the resulting RGB value.

Color Cyan Magenta Yellow R G B Dark green 255 180 255 255,75,0 0,255,0 0,75,

Tan 45 75 115

Blue-gray 80 60 45

4. Analyze: For each color in the table above, compare the cyan, magenta, and yellow values ( CMY values ) to the RGB values.

A. What is the relationship between the cyan value and the red value?

the red varies lower & higher in range

B. What is the relationship between the magenta value and the green value?

green varies higher than magenta value

C. What is the relationship between the yellow value and the blue value?

The blue one at first is the same then goes higher in value

5. Calculate: Use the Gizmo to check your answer.

What is the RGB value of a color with a CMY value of 30, 100, 0? cyan, 255, 255, 255 Magenta 255, 155, Yellow 255,255,255 = white

6. Summarize: In general, if you are given the CMY value of a color, how can you calculate the RGB value of the color?

Subtract all CMY colors by 255

7. Explore: Use the Gizmo to create a color matching each description. List the CMY value and RGB value of each color. Describe your own object and color in the last line of the table.

Description CMY value RGB value A dark blue night sky 255,255,105 0,0, A gray cloud 70,70,70 185,185, An orange pumpkin 0,135,240 255,120, A green olive 180,125,255 75,130, A red brick 0,255,255 255,0, 120,255,0 135,0,