# What Portion of the Mirror...?

 Materials: Computer and School Network Time Allotment: 3 Class Days

### Overview:

In this activity, you will use your understanding of the law of reflection and image formation in order to demonstrate what portion of a plane mirror is required for a person to view their own image. Additionally, you will utilize the paint tools of Hypercard to construct a ray diagram and further illustrate your understanding. You will summarize your findings by means of a word processed paper which includes pasted graphics from the Hypercard stack.

1. Log on to the server in the usual manner.
2. Open the HyperCard application found in the Multimedia folder.
3. From the File menu, choose Open... . A directory dialogue box will open. Navigate to the Physics Stacks and open the file titled Plane Mirrors.

Click anywhere on the title card of the stack, read the directions on the following card and click on the Start button. By so doing, you will navigate to the main card. A miniature snapshot of the appropriate card is shown below.

### Procedure:

1. Click on the Show Tools button. A palette of graphic tools will appear on the monitor. This palette can be relocated on the screen by clicking on the top bar and dragging it about. You will use these painting tools to construct a ray diagram showing how light travels from the top and the bottom of the person to her eyes in order for her to see her image in the mirror.
2. Use the tools to construct a ray diagram showing how light travels from the head and the toes of the person to her eyes in order for her to see her image in the mirror. Be as accurate as possible. Place arrowheads on all light rays in order to show which direction they are moving. Represent any extensions beyond the mirror by dashed lines. If necessary, use the information about Graphic Tools as found below. If you make an error which cannot be corrected by using the Undo function, then simply click on the New Object button.
3. Use the Measure button to measure the length of mirror needed to view the object of the given height. If necessary, repeat this measurement (or even your diagram) until satisfied with its accuracy.
4. Copy the diagram into the clipboard (use the Copy button). Immediately open a word processing document (or start a new one). Paste the diagram into the word processing document.
5. Repeat steps #1-4 above for two other object distances and object heights. Click on the New Object button to obtain a fresh screen.
6. Write up a lab report using the word processing document. The pictures which you have copied and pasted into the word processing document should be part of the Data section of the report. Your report should include the following sections:
• Purpose (a short description of what this lab attempts to accomplish)
• Procedure (a step-by-step discussion which explains how you attempted to accomplish your purpose)
• Data (a table which displays in row-column tabular form the data which you collected in this lab)
• Graphs and Diagrams (an organized and labeled display of any graphs or diagrams which support the conclusion of the lab)
• Discussion of Results (a couple of paragraphs in which you discuss the data, diagrams and the physics principles which were used to attain the diagrams and the physics principles which were revealed by attaining the diagrams)
• Conclusion (a single generalized statement in which you summarize what the experiment has proven)

### Help With Graphic Tools:

An explanation of each button at the bottom of the card can be seen by clicking on the Help button. The graphic tools in the "Tools Palette" can be used for showing the path light takes in traveling from the object to the mirror and then to your eye. Use these tools in order to construct a diagram to determine the portion of mirror required to view the image. To see the tools, click on the Show Tools button. The following explains the operation of the tools:

### Description of Use

Browse Tool

The browse tool must be active tool for clicking on all buttons. If you click on a button and nothing happens, select the browse tool from the Tools Palette by clicking on it.

Line Tool

The line tool can be use to draw a straight line between any two points. Click on the line tool to select it. To draw a line, click and drag the mouse so that a line is stretched across the monitor.

Eraser Tool

The eraser tool can be used to erase a given part of the diagram. If you wish to make a solid line into a dashed line (for example, the extension of a ray beyond the mirror), then select the eraser by clicking on it. Dragging the mouse across a part of the solid line will erase that part of the line. Doing this several times will give the line an appearance of being dashed.

Pencil Tool

The pencil tool can be used for a variety of purposes. Clicking at a point on the screen with the pencil tool will turn the color of that point from white to black or black to white. Holding down the mouse button and dragging with the pencil tool leaves a trace on the screen. The color of the trace will be the opposite of the color at the location where dragging began.

Pencil Tool + Command key

plus

The pencil tool can be used to "zoom in" on a particular part of the diagram to perform "pixel editing." Clicking on a particular part of the diagram with the pencil tool while the command key is depressed results in a magnified view of that part of the diagram. In this activity, the pencil tool can be used to zoom in on a ray and then to perform pixel editing to construct an arrow on the ray.