In this interactive simulation adapted from the University of Colorado's Physics Education Technology project, learn how lenses refract light to form images. Experiment with different ray display options (marginal rays or many rays) to investigate how a convex lens refracts light. Adjust the curvature, refractive index, and diameter of the lens to see how the focal length changes and how the resulting image is affected. Manipulate the placement of the object to observe its relationship to image size and location. This media asset was adapted from PhET: Geometric Optics.