A Diverging Lens: Always Virtual, Always Reduced

1 · Predict

A diverging lens has a negative focal length. Does it ever form a real, enlarged image, the way a converging lens can?

• No — a diverging lens always forms a smaller, upright virtual image, no matter the object distance.
• It forms a real image when the object is far enough away.
• It always forms a real, enlarged image.

2 · Set Up

1. Open the diverging-virtual preset and press Reset. The lens's focal length is fixed at −10 cm.
2. Enable the image-distance and magnification readouts.
3. Set the object distance for each trial and record the image distance and magnification.

3 · Collect Data

Plot magnification m (y-axis) against object distance d_o (x-axis) for your three trials. Does m ever exceed 1?

4 · Analyze

1. For one trial, compute d_i from 1/f = 1/d_o + 1/d_i using f = −10 cm, then m = −d_i/d_o. Compare both to the table.
2. Explain why, no matter how large d_o gets, d_i stays negative (virtual) and m stays positive and less than 1 for a diverging lens — unlike a converging lens's behavior in the converging-real experiment.

5 · Extend

1. A door peephole uses a diverging lens (or a similar wide-angle design) to show a reduced, wide field-of-view image of whoever's outside. Explain why a reduced image is exactly what you'd want for a peephole's purpose.
2. As d_o grows very large (object very far away), what does d_i approach? Compare it to the lens's focal length, and explain physically why a diverging lens's virtual image can never move past its own focal point.

The Physics Behind This Experiment

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