Why Do Mirrors Flip Left & Right (but not up & down)?

From Minute Physics.

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This video is about why words flip left & right (aka horizontally) in a mirror but not up & down (aka vertically). The answer has to do with specular reflection, mirrors being like windows into another world (alternate universes, just with in and out flipped!), and transparency of the things we write on.

Specular Reflection

PhysicsGirl video about mirrors

Fermat’s principle


Thomas-Fermi screening

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Created by Henry Reich