Math and Science Experiments



Math and Science Experiments

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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: smgriffi@indiana.edu

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.

Click the icon to obtain the free Reader.

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: mariavivirito@

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.

Click the icon to obtain the free Reader.

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 McGraw Hill.

Understanding the Primary Colors and Their Misconceptions!

An Educator's Reference Desk Lesson Plan

Submitted by: Heather Ingram

Email: hingram@indiana.edu

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).

2. Students will be able to demonstrate that the additive primary colors of light can be combined to form the secondary colors, namely cyan, magenta, and yellow.

Materials:

← chart showing the parts of the eye (see Internet site below)

← flashlights (each student should be provided with one that has a colored filter at the end of each head of the flashlight including the three primary colors: red, green, and blue)

← crayons/markers

← red, green, and blue cellophane to cover the flashlights

← tape

← extra paper (white paper)

← a big piece of white paper or a large blank screen

← pencils

← Venn Diagram Worksheet

←

← Venn Diagram Worksheet in .pdf format; requires free Adobe Acrobat Reader.

←

← Click the icon to obtain the free Reader.

Procedure:

Lesson Information:

Red, blue, and green are the primary colors of light. When lights of these three colors overlap on the same area (i.e. are added together), we see this area as white. These are also called the "additive" primary colors of light. The term "additive" indicates that as we add together more and more light of different frequencies, we eventually approach white light (red light + green light + blue light=white light). Other colors of light result by combining the primary colors in equal or unequal brightness. For example: cyan light = mix equal brightness of blue light and green light; magenta light = mix equal brightness of blue light and red light; yellow light = mix equal brightness of red light and green light; orange light = mix bright red light with dimmer green light.

Lesson Activity:

"If we shine three equally bright beams of red, blue, and green light onto a stage or screen so that the beams overlap, then we will observe different colors where two lights overlap, and we will observe white in the region where all three lights overlap (Have the children do this with their flashlights. Make sure that students put the correct colors together.). The reason that we can see colors is that there are special receptors at the back of the eye on the retina (show picture provided with the eye parts labeled on it, so that students can see it visually and have a better idea for the following information you will provide them with). These are called "cones" because of their shape. There are three types of cones. The first type is most sensitive to light in the lowest 1/3 of the visible range, allowing us to see red light. The second type of is most sensitive to light in the middle 1/3 of the visible range, allowing us to see green light. The third type is most sensitive to light in the upper 1/3 of the visible range, allowing us to see blue light. There are millions of each type of cone at the back of your eye."

Distinguish the primary colors of light and the primary colors of pigment from each other (i.e. painting verses using flashlights). Cyan, yellow, and magenta are the primary colors of pigment or paint. Ask students why they think that red, blue, and green are so unique. Explain again, that red, blue, and green are mixed to make all colors.

Fun information you can give to your students: "You can now relate this new information to computer monitors. Use a strong magnifying glass to look at a color television screen or color monitor on a computer. You will discover that the screen is composed of pixels of only 3 different colors: red, blue, and green. Inside the TV or monitor, beams of electrons are aimed at these pixels. Wherever the electrons hit, the pixels release that color of light. To see a white picture on your computer screen, the electron beams must simultaneously hit all three types of pixels, while only the red and green ones will be hit if you are looking at something which is yellow." Give students their own Venn diagram (see Materials ). Have them color and label the diagram using the information learned during the lesson.

Assessment: Collect students' completed Venn diagrams. Have the students try the flashlights again; it's always good to practice!

Useful Internet Resources: 
* The Eye and Its Parts 


* Explore Science: Additive Colors 
Allows the user to mix the following colors: red, green, and blue


* Explore Science: Subtractive Colors 
Allows the user to mix the following colors: yellow, cyan, and magenta


* Primary Colors of Paint, Ink, and Dyes 


* National Science Education Standards (NSES) 
 

Other Reference: 
Q202 Fall Semester Text: Physical Science for Elementary School Teachers (2002), Publication: Bloomington, Indiana at T.I.S. Bookstore. Reference Pages: 87-108.

Special Comments: You want your students to understand that the three primary colors are not red, blue, and yellow, rather they are red, blue, and green (this goes for primary colors of light, not pigment or paint). Students should use these colors and their concepts to create new colors using flashlights (these should be provided for the students with the red, green, and blue film covering the ends of the flashlight). Students should be able to demonstrate the new given knowledge of the primary colors of light by coloring a diagram (Venn diagram that is provided in this lesson plan. Make sure that you have enough copies for all of your students). Your students should be able to identify that there are not only primary colors of light, but also additive colors, colors which we make when we mix the primary colors together (cyan, magenta, and yellow). Your students should also be able to look at the eye chart and clearly see the parts of the eye (retina) and how these parts retain the colors that they are making. You want your students to ask as many questions about the confusions of these new facts that they are just now acquiring.

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