Seeing is Believing

Sarah Cersovsky

Spring1999

Cooperative Learning Lesson Plan

Teacher Information

Title of Lesson: Seeing is Believing
Standards:
Science --
Product -- optical illusions
Process -- observing
using numbers
communicating
identifying and controlling variables
constructing a model

Math --
Product -- fractions
Process -- communication
integration

Learning Styles:

tactile/kinesthetic
visual/spatial
interpersonal
logical/mathematical
sociological (group work)

Objectives:

Academic:
- The students will construct a Benham disk with 90% accuracy to demonstrate their knowledge of the presence of the color spectrum in white light.
Social Skills:
- The students will improve participation skills within a group.

Looks Like Sounds Like

leaning forward My idea is...
eye contact I think...
taking turns We could do...
smiles Good idea!
thumbs up That's interesting

Student Level: 3rd grade

Time Required: 35 minutes

Background Information:

The teacher needs to know the term "persistence of vision" to explain the Fish in the Bowl card (attention getter). One image remains, or persists, for a fraction of a second after the picture is gone.
The teacher will need to be aware of real life examples to make the term, "persistence of vision," relevant to the students. Examples: cartoon strips and motion on television. (A picture is changed 30 times per second).
The teacher will need to know how to construct a Benham disk and teach it to the students. A Benham disk is made out of a circle about 4-5 inches in diameter. One half of the circle is colored solid black and the other half is divided into four equal parts. In each part there are three curved lines, beginning at the outer edge of the circle in the first part and moving slightly inwards in each part after that. The disk is attached to a pencil eraser using a pin.
The teacher will need to know the colors that make up white light -- violet, indigo, blue, green, yellow, orange, and red.
The teacher will need to know that blue has the shortest rays and red has the longest rays.

Prerequisite Information:

The students will need to know basic fractions such as _ and _.
The students will need to know the difference between clockwise and counterclockwise.
The students will know how to participate in groups.

Materials:

Fish in the Bowl card
sample Benham disk
cardboard disk
white paper disks
black marker
pencil with eraser
pin
scrap paper
Benham disk project worksheet
group evaluation form

Group Size: 5 students per group

Roles: Materials

Constructor #1
Constructor #2
Recorder
Reporter
(All students will have a universal role -- encourager)

Teaching Procedure

Introduction of the Lesson:

Ask students to raise their hand if they have ever heard of the term "optical illusion."
Ask a student to tell the definition of an optical illusion. (A visual image that is deeply misleading or does not seem right).
Show students the card with a fish on one side and the fish bowl on the other side. Tell the students that you are going to spin the card in a forward direction. Ask the students what direction the card would be going if it were spun the opposite way (backward). Ask the students what direction the card would be going if it were turned to the right (clockwise). Ask the students what direction the card would be going if it were turned to the left.
Spin the card forward rapidly.
Ask students to explain what they see.
Explain to the students that one image remains for a fraction of a second after the picture is gone. (Briefly discuss basic fractions with the students -- "We know that a second is not very long. How long would _ of a second be? Would it be shorter or longer than one second? What about _ of a second? Would it be shorter or longer than a _ of a second?") When the card is spun fast, the new image appears before the old image is gone. The image of the fish and the image of the bowl merge into a single image of a fish in a bowl.
Tell students that this type of optical illusion happens all of the time and we do not even realize it.
Examples:
Cartoon strips -- a cartoonist will draw one picture then another with just a slight change. They draw many of these then stack them together. As they flip through them they can see motion. (Mixes one image with the next).
Motion on television -- "Did you know that the picture on a television screen is changed 30 times per second?"

Development of Concept:

Introduction-
1. Tell students that we will be doing an optical illusion project involving color.
2. "We will be working in groups for this project and it is very important for everyone to participate. Let's go over our participation t-chart that that we made last week."
3. Review t-chart. Remind students that we want everyone to participate. "Tell someone when they are doing a good job or have a good idea."
4. Put students into groups of five using construction paper strips with each of their names on them.
5. Tell the students that for this project we will be constructing Benham disks. (Show a sample of a Benham disk).
6. Explain the construction of the Benham disk.
  -Using a white paper disk, (What shape is a disk?) you will color _ of the circle black. The other half will be divided into four equal parts. ("I will show you an easy way to do that in a little while.") "In each of the four equal parts you will put three lines. These lines will be about as thick as your marker. In the first part, put your lines near the out edge. Move them closer to the middle of the circle in each part after that. To spin the disk we will place our white paper disk on our white cardboard disk. Push a pin through both disks and into the eraser. (Be very careful with the pins. They are very sharp!) Spin! First we will spin it clockwise. Watch closely and you will see something. Spin it counterclockwise and see if anything changed."
7. Explain the materials-
  -There are three white paper disks, two for constructing Benham disks (the second Benham disk will be their design) and one to fold to use as a pattern for sectioning the disk into fractions. (Show students how to do this.)
  -One cardboard disk in which we will place our white paper disk on. This cardboard disk will be used for both Benham disks.
  -A pencil for drawing lines and the eraser for attaching the disk.
  -Black markers for coloring the white paper disk.
  -Pins to stick through the disks and into the eraser.
  -Scrap paper to make sure that you do not color on the tables.
  -A Benham disk project worksheet in which each group will have to complete. (Briefly go over the worksheet).
  -A group evaluation form. (Briefly go over the evaluation form).
8. Go over Roles-
  Materials --
  In charge of getting materials and returning them at the end of the project.
  Constructor #1 --
  Constructs Benham disk #1.
  Constructor #2 --
  Constructs Benham disk #2.
  Recorder --
  In charge of filling out the worksheet and evaluation form.
  Reporter --
  Reports to the class what they found out. All group members are encouragers. "Remember, everyone needs to participate. If you need to look back up at the t-chart, go ahead."
9. Have materials people come get the materials.
10. Groups can begin the project (working on Benham disk #1).
11. When the groups are finished, ask the students what they saw. Go over the worksheet questions
12. Focus on question #3. (Why do you think this happened?) Explain to the students the reason we saw colors is because white light is made up of colors. "It is made up of violet, indigo, blue, green, yellow, orange, and red. These colors are also known as the color spectrum."
  -"The entire color spectrum is present in white light, but our eyes register the different colors at different lengths of time. When we spin the disk, the light from the colors that make up white reach the eye, but are visible for only an instant before being followed by the black portions of the disk. Our eye is only able to register a part of the color spectrum -- the blue, which has the shortest rays, and the red, which has the longest rays.
13. Have students construct Benham disk #2. (This disk should be different than the first one. _ of the circle still has to be black but the lines can be drawn in different places and also drawn in a different thickness.
14. Go over what the students discovered with Benham disk #2.
15. Finish project worksheet.
16. Clean up.
17. Fill out group evaluation forms.

Positive Interdependence:

Each student will be expected to fulfill his or her job/role in the group. Any problems will show on the group evaluation form.

Individual Accountability:

The students will perform their roles and participate in the group.

To check for participation, the teacher could ask any student a question about the group project.

Criteria for Success:

The students will construct the Benham disks and learn about the presence of the color spectrum in white light.

The students will participate in the group and evaluate their performance at the end of the lesson.

Expected Behaviors:

The students will fully participate in the group and encourage each other's responses.

Monitoring:

The teacher will call on various groups to report their findings and also to assure that the students are completing the project worksheets.

Processing:

The students will follow teacher directions to accurately construct Benham disk #1.

The students will encourage each other and evaluate their own performance in the group.

Conclusion:

Have the groups explain their findings for Benham disk #2 and discuss possible reasons why they were the same or different.

Have the students finish the project worksheet and evaluation form.

Evaluation:

While monitoring the students, the teacher will check to see if each group is constructing the Benham disk according to the directions. (If not constructed accurately, it may not work.)

The teacher will use both his/her observations and the group evaluation forms to determine if everyone participated in the project.

Extensions

To enrich the student's knowledge of this lesson the teacher could integrate another subject area such as literature. A book could be read at the beginning of the lesson to promote more interest. The students may also gain a better understanding if it were presented in another form.
To re-teach the concept of the color spectrum in white light, the teacher could use a prism. When light travels through a prism the color spectrum is visible.

Resources

Simple Science Experiments With Everyday Materials by Muriel Mandell. Sterling Publishing Company, Inc. New York. 1989.

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