Introductory lesson on lenses: The definition of a lens which involves transparency, shape, and affect on light.... The 4 general shapes of lenses, divided into 2 categories... The shape of a convex lens based on 2 prism's sitting base on base,and how light is refracted through each prism to a point... The principle parts of a convex lens which included the principal axis, the focal point, the focal length, the focal plane and the center of curvature...