A girl stands 1.2 m in front of a flat bathroom mirror. Where is her image and what kind of image is it?
A2.4 m behind the mirror, and it is virtual
B1.2 m in front of the mirror, and it is real
C1.2 m behind the mirror, and it is virtual
D0.6 m behind the mirror, and it is real
Answer & Solution
Correct answer: C. 1.2 m behind the mirror, and it is virtual
1. Applying the law of reflection to the rays that reach the eye shows that the image and object are the same distance from a flat mirror.
2. The girl stands 1.2 m away, so her image lies 1.2 m on the other side of the mirror surface.
3. The reflected rays only appear to originate from that point, so nothing can be caught on a screen placed there.
4. An image that cannot be projected is a virtual image, which rules out both real options.
5. Doubling the distance to 2.4 m confuses the object to image separation with the image distance itself.
_Source: OpenStax College Physics (CC BY 4.0), Ch 25 "Geometric Optics", section 25.7 Image Formation by Mirrors_
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