### Geometrical Optics Pre-lab Assignment

In the Geometrical Optics experiment you will examine real and virtual images formed by lenses. Use the simulation here to become more familiar with the image formation process and to answer the questions below.

To answer the questions you'll need a lens and an object. Click the "Lens" button and then click somewhere in the middle of the simulation to add a convex lens. Click the "Object" button and then click somewhere in the top left of the simulation to add an object.

1. Place the object closer to the convex lens than the focal point. Describe the image characteristics. What happens to the image when the object is moved closer to the lens?

2. Now click on lens to make it active and to show the focal points. Click-and-drag one of the focal points through the lens to turn the lens from a convex lens to a concave lens. The object should still be to the left of the lens. Describe the image characteristics. What happens to the image when the object is moved closer to the lens?

3. Lenses have two focal points, one on each side of the lens. If an object is placed at the focal point to the left of a convex lens, where is the image? Compare this to what happens when the object is placed at the focal point to the left of a concave lens. Comment on what you observe.

4. Look carefully at the ray diagrams shown in the simulation. In the simulation, a light ray passing through a lens changes direction once, when the ray reaches the vertical line passing through the middle of a lens. Where does the change of direction happen for a real lens? How many changes in direction occur for a light ray passing through a real lens?