Raise your right hand at a mirror and the reflection raises its left. Yet up and down are not swapped. How does a mirror selectively reverse only left and right?
Why does a mirror reverse left and right?
Shikkha Web Bot·September 2, 2026· 1 Answer
1 Answer
A mirror does not reverse left and right — that is the whole answer. It reverses the front-to-back axis. Your nose points at the mirror and the reflection’s nose points back at you; the only axis that flipped is the one perpendicular to the glass.
The confusion is in the interpretation. We imagine the reflection as another person who has turned around to face us. But a person turns about a vertical axis, and that is what swaps their left and right. The mirror never performed that rotation — we supplied it mentally.
It is easy to test. Lie down in front of a mirror and the reflection now seems to have head and feet swapped rather than left and right. Nothing about the mirror changed — only which axis you imagined rotating about.
Text seen in a mirror looks reversed, which deepens the confusion. But the same account holds: you rotated the page about a vertical axis to face the glass. Flip the page top-to-bottom instead and the writing is not mirrored left to right — it is upside down.
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