Figure 9 Convex lenses can form either real or virtual images. A When parallel incoming rays strike a convex lens, they are refracted toward each other and pass through the focal point. B When an object is located beyond the focal point of a convex lens, a real image is formed. C A magnified, virtual image is formed when the object is located between the focal point and the lens.
Convex lenses form either real or virtual images. Whether an image is real or virtual depends upon how far the object is from the lens. Figures 9B and 9C show a convex lens forming real and virtual images.
Convex lenses are used in slide and movie projectors, cameras, and lighthouses like the one in Figure 10. Of course, you don't see an upside-down real image at the movie theatre because the film is placed upside down in the projector. When the rays of light from the upside down film pass through the projector's convex lens, the real image is projected onto the screen right side up.
How is a convex lens shaped?
Figure 10 In the past, lighthouses used a light source placed at the focal point of a convex lens or series of convex lenses to form a beam of parallel light rays. Comparing and Contrasting How does the setup shown in Figure 9A compare with that used in old lighthouses?
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