Solve the mirror formula for a concave mirror, with a ray diagram.
Solve the mirror formula (1/v + 1/u = 1/f) for a concave or convex mirror, using the New Cartesian Sign Convention taught in NCERT/CBSE physics — enter plain positive numbers for focal length and object distance, and the correct signs are applied automatically based on which mirror type you pick, since manually remembering "object distance is always negative, focal length is negative for concave" is exactly the part most people get wrong under exam pressure.
The ray diagram is built using the same two-ray construction taught in every standard textbook: one ray leaves the top of the object parallel to the principal axis and reflects through the focus, and a second ray passes through the center of curvature and reflects straight back along itself. Where these two rays actually meet (or where their backward extensions meet, for a virtual image) is the top of the image — this tool draws both rays and verifies they agree with the algebraic answer from the mirror formula, the same cross-check a textbook diagram is meant to demonstrate.
A solid image arrow means a real image (light rays actually converge there, and it could be projected on a screen); a dashed image arrow means a virtual image (the rays only appear to diverge from that point, and it can't be projected, the way your reflection in a flat mirror can't be caught on a screen either).
Because that’s exactly where most sign-convention mistakes happen — forgetting that object distance is always negative, or that focal length’s sign depends on mirror type. Entering plain magnitudes and picking the mirror type from a dropdown means the correct signs are applied for you automatically, every time.
This happens when the object is placed exactly at the focus of a concave mirror — the reflected rays become perfectly parallel and never converge, so there’s no finite image distance. This is a real, well-known result, not an error.
This is a genuine property of convex mirrors, true for every object position — unlike a concave mirror, where the image type depends on exactly where the object is relative to the focus and center of curvature.
Yes — that’s the whole point of the construction. Both rays are calculated independently from the object’s position and the mirror’s focal length, and if the geometry and the mirror formula agree (which they will, since both come from the same underlying physics), they meet at precisely the algebraic image position.