An image of magnification m = +1 will be produced by:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → a plane mirror only.
The magnification is m = h′/h. A value of m = +1 means the image is erect (hence virtual for a single mirror or lens) and exactly the same size as the object.
A plane mirror always forms a virtual, erect image of the same size, as far behind the mirror as the object is in front, so m = +1 for every position of the object.
Why the other options are incorrect
Option (2) a plane mirror and a convex lens — Incorrect. A convex lens forms an erect image only for an object within its focal length, and that image is always magnified (m > 1).
Option (3) a plane mirror and a concave mirror — Incorrect. A concave mirror forms an erect virtual image only for an object between P and F, and that image is magnified; at C it forms a same-size image, but it is inverted, so m = −1.
Option (4) a concave mirror only — Incorrect. As shown for Option (3), a concave mirror never gives m = +1.