When will the light rays become a convergent light rays

Q: When will the light rays become a convergent light rays?

You can produce convergent light rays by passing abeam of light through an optical instrument that is equipped with a focussing lens.
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Q: And what is the property of the convergent light rays

A convergent light ray will produce a real image that can fall on a screen.
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Q: What is the different between convergent light rays and parallel light rays?

Parallel light ray forms an image at infinity, whereas convergent light ray produces a real image.

after passing a convex lens