Why do mirrors reverse left and right but not up and down?
In: Physics
Wear a shirt with some words on the front. Bend sideways at the hip so you’re facing the mirror with your torso sideways. The words on your shirt will now be “up and down reversed.”
The mirror will always reflect light so that the angle of light arriving (“angle of incidence”) will equal the angle of light reflection.
With pieces of yarn and some tape, you can even mark off the 3-D geometry between the letters on your shirt and the reflection in the mirror to show that there’s no geometrical left-right tricks going on.
Some people sum that up by saying “You were the one who swapped the letters left-right, when you put the T-shirt on. You started off looking at the face of the shirt to read it, then you flipped it around before putting it over your head.”
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