This tutorial examines how variations in the refractive index of both lens materials and imaging media affect the focal point of a bi-convex lens.

	Interactive Java Tutorial
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To operate the tutorial, select the lens material from the left-hand side pull-down menu. As the refractive index of the lens material increases, the focal point will move closer (to the left) to the lens. The right-hand side pull-down menu controls the refractive index of the imaging medium. As the refractive index of the imaging medium increases, the focal point moves farther away (to the right) of the lens.