What is the difference between converging and diverging lenses? How is the shape different?

A converging lens is said to have positive focal length. A converging lens causes exiting rays to be more convergent coming out than they were entering the lens. A diverging lens is said to have negative focal length. ... A converging lens can form a real image or a virtual image of a real object

Explanation:

a tetrad is the foursome during meiosis made by two homologous chromosomes that have each already replicated into a pair of sister chromatids.