This simulation deals with the formation of images using a lens or a mirror. You can set the object distance, the object height, and the focal length of the lens or mirror. The simulation shows the paths followed by the light rays, illustrating how images are formed.

To change the position or size of the object, or the shape of a mirror or lens, place the mouse pointer over one of the colored dots in the simulation. When the pointer changes to a hand, click-and-drag. Do this with the dot at the tip of the object to change the object height and/or object distance; with the dot at the center of the lens or mirror to move it left or right; and with any focal point (F) to change the shape of the mirror or lens.

Here are some things to investigate:
1. What are the image characteristics when a plane mirror is used? Is the image real or virtual? Is the image upright or inverted? How do the image height and the image distance compare to the object height and the object distance?
2. What are the image characteristics when a diverging(convex) mirror is used? If the object is moved closer to the mirror, what happens to the image?
3. There are many similarities between an image formed using a diverging(convex) mirror and an image formed with a diverging lens. Compare the two situations. What similarities do you observe? What are the differences?

The case of a converging mirror or lens is more complicated than a diverging mirror or lens. The image can be real and inverted, or virtual and upright; it can also be larger, smaller, or the same size as the object. By changing the object distance, determine what range of object distances corresponds to each of the following cases:
1. A real image smaller than the object.
2. A real image the same size as the object.
3. A real image larger than the object.
4. A virtual image (is the image always larger, smaller, or the same size as the object?)