# What do we actually mean by parallel rays when talking about reflection from a concave mirror? [duplicate]

If we place a point object at the focus of a concave mirror, we say that the reflected rays would be parallel and would meet at infinity to form an image.

What does this mean?
I tried to trace the reflected rays using the rules of image formation using a concave mirror and I got two rays almost parallel (negligible convergence). This could have been (and probably was) a construction error since achieving precision by hand is quite a difficult task to perform.

So, when we say that the reflected rays are parallel, do we mean that they are almost parallel and would meet at a lot of distance from the mirror? Is that also why we say that they will meet at infinity?

Thanks!

• Does this answer your question? What does it mean to say image is formed at infinity? – FakeMod May 5 at 11:09
• It does answer a major part of it but I need some confirmation. So, this means that the light rays are exactly parallel and no image is formed, right? – Rajdeep Sindhu May 5 at 11:14
• "So, also the image is never really formed, we still say that "the image is formed at infinity" just to maintain the symmetry of the problem. However, since this can never be measured, the wording is only a convention, not an experimental fact." – FakeMod May 5 at 11:15
• Thanks! And, what about when the object is placed at infinity? I know that $X_i$ and $X_o$ are interchangeable. But how would one explain it visually? – Rajdeep Sindhu May 5 at 11:21
• The image will be formed at the focus. – FakeMod May 5 at 11:22