Optics Lens Diagram. Where the two lines cross the object appears. The way light bends when it goes from air to a different material such as water or glass is called refraction.
Draw a line all the way from the tip of the object straight through the center of the lens to the other side. Rather than go into the theory let. The use of multiple elements allows more optical aberrations to be corrected than is possible with a single element.
Use a ruler to follow the arrow tip lines back to the virtual side of the lens.
For example in zoom lenses where ten or more lens elements are typically used two aspheric lenses can be substituted for a handful of spherical lenses in order to achieve similar or better optical results while reducing system size and potentially reducing the overall cost of production. Description simulation of image formation in concave and convex lenses. Examples are given for converging and diverging lenses and for the cases where the object is inside and outside the principal focal length. They are used by humans to observe very tiny microscope and very far away telescope objects.