This tutorial explores the effect of lens shape on the interaction of a lens with light. Each side of the "window" is adjustable to produce a concave or convex surface using the sliders below.

	Interactive Java Tutorial
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This applet also considers refraction, convergence, and divergence of light as it passes through the lens from the left-hand side of the applet. Important values are delineated on the optical axis of the lens(es). The values F and F' are real and imaginary focal points (respectively), O is the object being imaged and I is the point where the image occurs. In situations where a real focal point occurs, the effects of optical aberrations are illustrated as separately colored (red and green) lines of focus.