## My World Is Upside Down

### John LienOrange County Schools

#### Description

Students make a pinhole viewer to demonstrate that even though light travels in oscillating waves through space, the wave lengths are so small that light behaves as traveling in a straight line.

#### Objectives

The student describes and compares the properties of particles and waves.

#### Materials

For each group of 2-4 students:
-2 Pieces of heavy paper
-Aluminum foil
-Wax paper
-2 Rubber bands
-Pin
-Tape
-Light source (classroom light or the sun)
-My World Is Upside Down lab sheet (See Associated File), 1 per student

#### Preparations

1. Make example pinhole viewer. (See Associated File for graphic illustration, top of page 2)
2. Make copies of lab sheet. (See Associated File)
3. Make transparency of image for attention getter. (See Procedures, step #1)
4. Assemble students into small groups of 2-4.
5. Organize all materials for each group in individual small tubs or baskets for easier and faster distribution of materials.

#### Procedures

Note: This activity covers only the property of light waves as they travel.

1. To engage the students to learn about light, try this quick and easy demonstration. Wrap a meter stick in white paper. Aim an overhead projected image toward a wall with lots of distractions or a corner. Focus the image on a piece of paper a few feet from the projector (the image doesn’t have to fit on the paper, just be in focus). Only a blurred image should appear on the wall, and students shouldn’t be able to make out what it is. The sharp, real image is still there in space, but can’t be seen because the light from it is not reaching the viewer’s eyes. Now hold the meter stick in the same place that you focused the image on the paper. Viewers will see a small piece of the image in focus. Move the meter stick to a new position and viewers will see a different piece. Now move the meter stick up and down rapidly, and the whole image will be seen! The sharp image appears to float in space. This works because the human visual system is able to retain an image for a fraction of a second. As you move the meter stick quickly up and down, the images all appear to be a continuous image.

2. Students should be familiar with the following information: Light emitted by a luminous object travels in a straight line outward in all directions from the source. When an obstruction with a small hole is placed in the path of the light, the light will travel in a straight line through the hole. Light travels from the top of the object in a straight line through the hole, and strikes the bottom of the screen. Likewise, the light from the bottom of the object travels in a straight line through the hole and strikes the top of the screen. This produces a real but inverted image. When the hole is enlarged, the image will become blurry. Since more rays will be able to pass through the bigger hole, the image will appear sharp.

3. Prior to class, organize all materials for each group in individual small tubs or baskets for easier and faster distribution of materials.

4. Have one student from each group pick up the tub or basket of materials.

5. Review the construction process (steps 6-12 below) with students. Be sure they understand it. If you prefer, have all students build the viewers at the same pace as you lead the class. Review safety when using sharp objects. (See the Safety Concerns section of the lab sheet)

6. Roll a piece of the heavy paper to make a tube. Tape the seam to secure the tube.

7. Cover one end of the tube with wax paper and tape it to the tube.

8. Place the second piece of paper around the outside of the tube so that it forms a second tube.

9. Tape the second tube so that it forms a tube that can snugly slide over the end with wax paper and slide it enough so the end with wax paper is inside the second tube.

10. Cover the end of the second tube on the side of the wax paper with foil, and secure it with a rubber band. (See Associated File for graphic illustration, top of page 2)

11. As students build their pinhole viewer, circulate in the classroom to provide assistance.

12. Poke a small hole in the foil with a pin. (See Associated File for graphic illustration, top of page 2)

13. Hold the foil end up to light source such as a window and look through the uncovered end of the inner tube. You may adjust the focus by moving the inner tube back and forth.

14. You will need a bright light. If you have good overhead lights in the classroom, students should be able to see that the lights' image is upside down. If it is bright outside, students should be able to see regular objects.

15. Students make observations using their pinhole viewer and record observations on lab sheet.

16. Students then make the hole a little larger and continue to record their observations.

17. Students then make 2 holes in the viewer and record their observations.

18. As students are working in their cooperative lab groups, circulate to each lab station to monitor student progress and to facilitate critical thinking. Once students complete the lab investigation, they must answer the critical thinking questions located at the end of the lab. (See Associated File)

#### Assessments

1. The My World Is Upside Down lab sheet, containing critical thinking questions, is used as a formative assessment for students to identify the property of light to travel in a straight line. (See Associated File) It is also used to assess students’ ability to use appropriate experimental design, with consideration for rules, time, and materials required to solve a problem.

2. A Standards Checklist (See Associated File) will be used by the teacher to assess students' ability to work cooperatively and if they demonstrate creative and critical thinking skills to solve a problem. Print the checklist on a separate paper for teacher use. You may copy and paste several tables on a page to save paper, also you can use it for individual students or as a group.

#### Extensions

If materials are available, allow each student to construct his/her own viewer.

#### Attached Files

This file contains the My World Is Upside Down lab sheet and the Standards Checklist.     File Extension: pdf