Locate the image position of point source O in adjacent diagram

Is it clear now
Image is clear, but what is the straight line showing?
plane mirror, concave or convex mirror, lens? which one?
Yes it is straight lines showing
It is plain mirror
for plane mirror, focal length is infinity. F1 and F2 are wrongly shown in diagram


For plane mirror, the image is formed at a distance same as the object distance but in the opposite side of the mirror.
So if distance of point O from mirror is D, then object is at a distance D
So image will be formed at a distance D on opposite side.

Note that the image is virtual. Real image is not formed.

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