Question

The position of the object at the Focus,then what is the nature and size of the image? ​

Answer 1

Explanation:

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When object is placed at Principal Focus (F) of a concave mirror, image is formed at infinity. This is just opposite of the position of object at infinity.

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Answer 2

Explanation:

if it is a convex lens the position of the object is at focus the nature of the objective will be real and inverted