Question

how to we know that when we put an object on focus the image is formed at infinity?What is infinity here?

Answer 1

Answer:

By definition, the rays stay parallel and go on to infinity when light from an object originates exactly at the focal point. The rays technically shouldn't focus, but practically moving the lens just a millimeter or so can get an image focused on a far away screen the way a projector does.

Answer 2

By definition, the rays stay parallel and go on to

infinity when light from an object originates exactly at the focal point. The rays technically shouldn't

focus, but practically moving the lens just a millimeter or so can get an image focused on a far away screen the way a projector does. So depending how precise your placement is, you could get a clear, fuzzy, or no image on a screen say 20 feet away. As

the screen gets farther away, your image gets larger and dimmer, so it couldn't form a real image at a very

far distance anyway let alone infinity. It has just

become an expression to say an image is "formed"

even though an image is never formed since you can

never reach infinity. It would similar to saying that

parallel lines "meet" at infinity, but that would

contradict the meaning of "parallel". A better description would be to say that an image if formed very far away as an object approaches the focal

point.

hope it helps!!!

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