The mirror is either plane or convex.

Quick Scoop

When your image stays always erect no matter how near or far you stand from a mirror, it rules out a concave mirror.

  • A plane mirror always forms a virtual, erect image of the same size as you.
  • A convex mirror always forms a virtual, erect image that is diminished (smaller than you) but still upright.
  • A concave mirror gives an erect image only when you are very close (between pole and focus); at larger distances it makes your image inverted, so it cannot match the “erect at all distances” condition.

So, in standard exam and textbook questions, the correct option is:

Either plane or convex.

Why this is a popular question now

This type of question appears frequently in competitive exams and school tests (CDS, CBSE-style papers, and coaching material), so it often trends on Q&A and forum sites where students discuss physics and exam prep.

TL;DR: If your image is always erect at any distance from the mirror, the mirror is likely either plane or convex.

Information gathered from public forums or data available on the internet and portrayed here.