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Light Additive Subtractive Color
Exploratorium Science Snacks About Light
The Color of Light
Grade Level: 4 - 6
Discussion:
Ask your students what color they think light is. A silly question? Sunlight or light from a lamp may look "white" but it is really made up of different colors. Red, blue, and green are the primary colors of light. That means you can make any color from combinations of these three. We see an object in a certain color because that color is reflected by the object, while other colors are absorbed.
Materials:
3 big flashlights, pieces of red, blue, and green cellophane paper tape 30 cm white card white toy or ornament
Procedure:
1. Tape one piece of cellophane over the bulb end of each flashlight.
2. In a dark room, turn on the flashlights.
3. Shine the red and green flashlights on to the white card. What happens? (You make the color yellow.) Try mixing the blue and green lights. (You get cyan.) Now mix the blue and red lights. (You get magenta.)
4. Put the white toy in the center of the card and shine the three flashlights on it. Have the students circle around the toy to see it in different colors.
5. Ask them what color you will get if you shine all three lights on the white card at the same time. (You get white. White light is made up of red, blue, and green. These are called the primary colors. To get black, you would have mixed colored paints, not lights.)
Primary Colors: Additive and Subtractive
Additive Subtractive Color
Submitted by: Stacy Griffith
Email:
School/University/Affiliation: Indiana University School of Education
Endorsed by: Deborah Hanuscin
Indiana University
Date: December 9, 2002
Grade Level: 3, 4
Subject(s):
Science/Physics
Arts/Process Skills
Duration: Two 30-45 minute sessions
Description: The purpose of this lesson is to introduce students to the additive and subtractive primary colors and to correct the misconception that red, yellow, and blue are the "primary colors."
Goals: Indiana Academic Standards : (Science: Grade 3) Standard 1: The Nature of Science and Technology
The Scientific View of the World
3.1.1 - Recognize and explain that when a scientific investigation is repeated, a similar result is expected.
Scientific Inquiry
3.1.2 Participate in different types of guided scientific investigations, such as observing objects and events and collecting specimens for analysis.
3.1.3 Keep and report records of investigations and observations using tools such as journals, charts, graphs, and computers.
3.1.4 Discuss the results of investigations and consider the explanations of others.
The Scientific Enterprise
3.1.5 Demonstrate the ability to work cooperatively while respecting the ideas of others and communicating one's own conclusions about findings.
Objectives:
Students will be able to name the additive primary colors of light (red, blue, green) and the subtractive primary colors of pigments (cyan, magenta, yellow).
Students will be able to demonstrate that the additive primary colors (of light) can be combined to form white light.
Students will be able to demonstrate that yellow, cyan, and magenta are subtractive colors (meaning one of the primary colors of light is missing) using colored filters and flashlights.
Students will be able to predict the resulting color when two or more colors of light are combined.
Materials:
slide projector
white screen
prism
6 flashlights with batteries: (can be bought at Wal-Mart, Target, or other department stores)
scissors
pencils
colored filters (red, blue, green, cyan, magenta, and yellow -- can be ordered from Edmund Scientifics Company - Tel: 800-728-6999)
Worksheet and Answer Key
Worksheet and Answer Key in .pdf format; requires free Adobe Acrobat Reader.
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Vocabulary:
additive primary colors (the primary colors of light) - red, blue, and green
subtractive primary colors (the primary colors of pigments, dye, or ink) - cyan, magenta, and yellow
Procedure:
Teacher Preparation:
Each group of students should have 6 flashlights and 6 colored filters (red, green, blue, magenta, cyan, and yellow). Depending on the level of students, each group of students should cut out circles that will cover the flashlight's light with each different colored filter. The flashlights can be taken apart, and the clear plastic cover traced. The filter should be placed on top of the clear plastic cover when then flashlight is put together. (Teachers may choose to do this ahead of time, especially if they do not have the financial capability to have enough supplies for several groups.) Each group will also need a space in the room with a large white piece of paper hung on which they can shine the flashlights.
Teacher Background:
Ask the students what they know about the primary colors. Students may believe that red, yellow, and blue are the primary colors because when they mix blue and yellow paint they get green. While we know that this process works and is used in art classes, it is not scientifically accurate. If these were truly primary colors, we would not be able to create them by mixing other colors; however, if we mix red and green light, the resulting color is yellow. Similarly, if we mix magenta and yellow light, the resulting color is red. Clearly there's more to it than this! The additive primaries, or the primary colors of light, are red, blue and green. These combine to form white light. If we subtract each of these colors, one at a time, from the white light, we end up with the subtractive primary colors, or the primary pigments—cyan, magenta, and yellow:
red light + green light + blue light = white light
white light – red light = cyan light
white light – green light = magenta light
white light – blue light = yellow light
In this activity, students will explore the additive and subtractive primaries using colored lights. It is important that teachers do not simplify the names of the colors, calling cyan "blue" or magenta "purple"—scientifically, in terms of the spectrum of visible light, cyan and blue are two very different colors, as are magenta and purple.
Teacher-guided Exploration: Place a slide projector in front of a white screen. Turn on the projector. Position a prism in front of the light. Place the screen at a shallow angle intercepting the light, so that the rainbow is spread over a greater distance. This makes it easy to see the colors. When light travels through the triangular-shaped piece of glass, the light bends or changes direction when it enters the prism and when it leaves the prism. This is called refraction. Different frequencies or colors of light change directions by slightly different amounts, so the red frequencies change direction less than blue frequencies. As a result, the narrow ray of white light which strikes the prism is broadened out in space according to the different frequencies contained within the white light, and we see the familiar rainbow. This is essentially how a real rainbow is produced; water droplets replace the glass prism. Have students look closely at the rainbow so that they are familiar with the colors which constitute white light (red, orange, yellow, green, blue, indigo, and violet) and so that they see how the spread of colors is continuous. Now place a colored filter, one at a time, between the slide projector and the prism. The prism will display the frequencies of light which are able to pass through the filter; observe the gaps in the rainbow for those frequencies which were not able to pass through the filter. Now students should be able to see that red passes through a red filter, blue passes through a blue filter, and green passes through a green filter. (Make a chart if it helps.) Student Exploration: After all of the materials are ready, each group of students should first take the red covered flashlight and shine it on a large, white piece of paper that is taped to the wall. They will observe that the color that appears is red. They will do this for all of the colors/flashlights. Now the students should shine the red, blue, and green lights together to observe that the new color is white (Note: the color may appear slightly grayish depending on the quality of your filters and/or the spectrum of light emitted by the flashlight bulb). The teacher should next ask students to explore what color light they observe when they subtract each color one at a time from the white light they created. The teacher may take oral responses from the students, or depending on the age of the students, instruct student groups to make a data table to record their findings. Tying it all Together: Gather groups together to share and compare results and observations. Note any discrepancies in data, and re-check using flashlights again if needed. Students should have noted that red, green, and blue light combine to make white light. Now the teacher can explain why we call these ADDITIVE primary colors! The teacher can then explain that by subtracting a primary color from white light, you can obtain yellow, magenta, or cyan. This is why these colors are called SUBTRACTIVE primary colors.
Assessment: Give each student a worksheet (see Materials ). The worksheet has circles for red, blue, and green. Students will determine where two primary colors meet and identify in the smaller circles what color is apparent.
Useful Internet Resources: * Primary Colors of Paint, Ink, and Dyes
* Indiana Academic Standards * Edmund Scientifics Special Comments: Perhaps you were taught that the primary colors are red, yellow, and blue. Maybe your own elementary teacher thought that "cyan" and "magenta" were too difficult for you to pronounce. This simplification, however, has resulted in scientific inaccuracy, and widespread misconceptions-- complicated by the fact that artists use these as the primary colors of mixing paint. However, a simple check of the color printer cartridge will reveal that cyan, magenta, and yellow are indeed used as the primary inks for printing color!
Light and Color
An Educator's Reference Desk Lesson Plan
Submitted by: Maria Vivirito
Email:
Endorsed by: Bernard Poole
University of Pittsburgh at Johnstown
Date: January 29, 2003
Grade Level: 8
Subject(s):
Science/Physics
Duration: 50 minutes
Description: This lesson explores the colors of light and pigments by illustrating the use of the visible light spectrum in our everyday life. Students will be able to identify the relationship between color and light.
Goals: Pennsylvania Academic Standards for Science and Technology :
3.4. Physical Science, Chemistry and Physics
7.B. Relate energy sources and transfers to heat and temperature: Know that the sun is a major source of energy that emits wavelengths of visible light, infrared and ultraviolet radiation.
Objectives:
Students will be able to define opaque, transparent, and translucent and describe the differences between them.
Students will be able to describe how the different waves of light create color and why we are able to distinguish all the colors of the light spectrum.
Materials:
"shoebox of fun" (A shoebox with a eye-hole cut out of one end and a square cut out on the lid. Cover the hole on the lid with red cellophane. Inside the box glue down three gumballs -- red, green, and white.)
overhead projector
paper
pencils
Transparencies
Light and Color: Handout
Homework Assignment
Transparencies, Handout, and Homework Assignment in .pdf format; requires free Adobe Acrobat Reader.
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Procedure:
Attention Getter: (5 min.)
Have students look into the "shoebox of fun." What do they see? Students write down their answers on a piece of paper and set aside.
Review: (5 min.)
Go over the previous class lesson (wavelengths). Write the spectrum on the board in order of decreasing wavelength (radio, infrared, visible light, ultraviolet, x- ray, Gamma rays).
Lecture: (10 min.) Set up the scenario of waking up in a dark room. [ Author's Note: I simply tell the students a story about my morning routine of waking up in a dark room and then opening up my curtains to let in sunlight. I explain why I can't see anything until I let light in. This sets me up to talk about opaque, transparent, and translucent materials.] Different types of matter let in different types of light. Define the following:
opaque - Material that absorbs or reflects all light and you cannot see objects through them. (Example: curtains) Ask for another example!
transparent - Allows light to pass through and you can clearly see objects through them. (Ask the class for an example, such as a transparency!)
translucent - Allows light to pass through it but you cannot see objects clearly through it. (Example: frosted glass)
Transition:
"All matter has color. Do you think light has anything to do with color?" On the board, break down the light section into colors. "Light is made up of all the colors in the rainbow (ROY G BIV). There are three primary colors of light (make up all the other colors): red, green, and blue. Red + green + blue = white light. (Refer to the transparency on light, in Materials ). When we see a color, that means the object repels that color and absorbs all the other colors of the spectrum. So if something is white, what colors does it absorb? If we see light blue, what colors are absorbed? What about yellow and pink?"
Discussion: (5 min.)
Refer back to the box and have students hypothesize what is going on in the box, using the knowledge they now have. Refresh students' memories about what they saw in the box. Reveal what is inside the box. Have students hypothesize why the balls are not the colors that they saw with the lid on. "What kind of light was coming in the box with the lid on? With the lid off?" The lid acted as a filter. A filter is a transparent material that transmits one or more colors of light and absorbs all the other colors of the spectrum. "Why do you think the green balls looked black?"
Individual Exercise--Mixing of Colors: (at least 5 min.)
Place the primary color transparencies on the overhead. Have students take out a piece of paper. Ask, "Why does the mixing of the three colors give you black? What is happening to white light?" Students write their ideas on a piece of paper.
Discussion: (5 min.)
When everyone is finished, ask for a volunteer to answer the questions. Get several students' feedback. Define the term pigment : colored material that absorbs some colors and reflects others. Mixing of colors is used in our everyday life (Example: Sunday comics).
Handout: (10 min.)
Divide students into pairs and have them complete the "Light and Color" handout.
Conclusion: (5 min.)
Have students return to their seats. Ask for volunteers to share their answers to the questions on the handout. Go over any final questions that students may have.
Assignment:
Give students the homework sheet (see Materials ); it will be due the next class.
Assessment: Observe students' participation in activities and discussions. Collect students' handouts and homework assignments to check for accuracy and completeness.
Useful Internet Resource: * Pennsylvania Academic Standards for Science and Technology
Other Reference: Physical Science by Thompson, McLaughlin, and Smith; Glencoe/MacMillan McGrawHill.
Understanding the Primary Colors and Their Misconceptions!
An Educator's Reference Desk Lesson Plan
Submitted by: Heather Ingram
Email:
School/University/Affiliation: Indiana University
Endorsed by: Deborah Hanuscin
Indiana University
Date: December 29, 2002
Grade Level: 4, 5, 6
Subject(s):
Science/Physics
Arts/Process Skills
Duration: 60-90 minutes
Description: This lesson plan teaches the primary colors of light and how our vision allows us to detect these colors. The activities are intended to address the misconception that primary colors are red, yellow, and blue.
Goals:National Science Education Standards (NSES) : Content Standard B: As a result of the activities in grades K-4, all students should develop an understanding of
Properties of objects and materials
Position of motion and objects
Light, heat, electricity, and magnetism
Objectives:
-1.Students will be able to name the additive primary colors, or primary colors of light (red, blue, and green).