# To observe image formation by thin lenses and to compare results with those given by the simple lens equation.

Essay by lemon_tea812University, Bachelor'sA+, June 2004

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Objective: To observe image formation by thin lenses and to compare results with those given by the simple lens equation. Also measure the focal length of a converging lens. use this lens to form real images and to compare the measured position of each image with theory. And, also use the lens to observe a virtual image, estimate is magnifying power, and compare with theory.

Theory:

The focal point of a converging lens is defined as that point where a beam of incoming parallel light rays will be brought to a focus. For a diverging lens, a beam of parallel light rays will be spread out such that it will appear to diverge from a focal point located in front of the lens. Since lenses can bend light rays as stated above, it is therefore possible to form images using lenses. The location and nature of an image formed by a lens can be predicted either from a ray tracing diagram or by means of a lens equation.

Equipment:

Diverging Lens

Lamp

Ruler

Procedure:

1) Measure the focal length of your converging lens by placing a lighted object on one side of the lens, and a viewing screen on the other.

2) Adjust the positions of the lens and screen until the object and the focused image are the same distance from the lens. Under these conditions the focal length will be one-half the object distance (or one-half the image distance since they are the same in this case).

3) Measure carefully for predictions.

4) Position a lighted object on the optical bench at each of the distances specified in procedure.

5) Locate the image on a viewing screen and measure the image distance in each case. Compare your measured results with the results predicted in procedure.

6) Find the...