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Inquiry: Parabolic Mirrors

Purpose: To study the images formed by concave mirrors

Procedure:

Case 1:

Determine the focal length of the concave mirror by projecting the image of the sun on a small screen, and carefully measuring the image distance from the vertex of the mirror. If a direct view of the sun is not obtainable from the laboratory, the sharply defined image of a distant object outside the laboratory window will give a close approximation of the focal length of the mirror. Record 1/f in your science notebook.

Case 2:

Set up the meter sticks and concave mirror as shown above. The apex of the V should be slightly below the center of the mirror. Mount the light source on one meter stick as far away from the mirror as possible. Measure the distance from the mirror to the FRONT of the light source and record it as so. Mount the image screen on the other meter stick and move it back and forth until a sharp image of the light source is obtained. Measure the distance between the mirror and the image screen and record it as si. Measure the height of the object (the letter F) and record as ho in your notebook. Measure the height of the image and record it as hi. Determine all of the variables in the table below and record in your notebook to the degree of precision permitted by the metric scale you are using.

Case 4:

Interchange the light source and the image screen so that your light source is now closer and your image is farther away. Make any necessary adjustments in the position of the image screen so as to obtain a sharply defined image. Determine all of the variables in the table below and record in your notebook to the degree of precision permitted by the metric scale you are using.

Case 3:

Find the position of the light source and screen for which ho and hi are equal and record all your values in your notebook.

Case 5:

Move the light source so that so is equal to the focal length of the mirror. Can you locate a real image?

Case 6:

Move the light source so that it is inside the focal length. Look into the mirror and examine the virtual image. How does its height compare to the height of the object?

Inquiry Questions:

  1. In your notebook, using a 1.0 cm tall vector object and a 5.0 cm focal length mirror, create ray diagrams of all 6 concave cases as well as the convex mirror case. Label the geometric ray lines you used and compare the measured image location to the calculated image location from the MIRROR EQUATION for each case.