Question

What happens if you place a concave lens on the focal point of a convex lens​

Answer 1

Explanation:

if you place a concave lens on the focal point of a convex lens because of the negative focal length for double concave lenses, the light rays will head towards the focal point on the opposite side of the lens. These rays will actually reach the lens before they reach the focal point. ...

Note that the two rays refract parallel to the principal axis.

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