One might wonder why is it that when you see writing through a mirror that the writing is backwards, but not upside down. Here we try to understand why it is we see objects in reflected from mirrors as we do.
When one looks into a mirror it appears as if you are looking through it and seeing the object on the other side. It also seems as if the object is flipped left to right. In reality the right half of the real object is on the same side as the right half of the virtual object.
To prove to yourself that this is true, stand in front of a mirror. Now make a movement with your right hand, or wink your right eye. Looking at yourself in the mirror, from your viewing perspective, was the image of the hand (or the eye) on the right or the left that moved?
Let's define some terms. By real object
(image) I mean the object that is being
reflected. By virtual I mean the image or
the reflection of the real object.
When you hold words in front of a mirror by standing behind the text (as I am, below) and look at its reflection, the right side of the reflected word will be on your right side and will appear backwards. If I was actually standing with the sign in front of you, the words, from my perspective, would read from right to left because I am behind the sign. They would read from left to right for you, as does this text on the video monitor.
By the way, have you ever noticed that Ambulances use this illusion by writing the word "Ambulance" backwards on the front of their vehicle. They do this because when you see the vehicle through your rearview mirror the word Ambulance appears normal and then you are absolutely certain about what is behind you.
Up down is not a problem because the reflected image is up just as you would expect it to be if the object was really opposite you.
If you are still doubtful as this explanation lets look at the following photo which I took of myself in front of a mirror.
The forefinger of my right hand is on the camera button that takes the photograph. Notice that it is on your right. Now if I was really facing you, i.e. not reflected from a mirror, the forefinger on the button would be on your left side. You might not like taking that on faith.
So, take a look at the writing across my sweatshirt. Obviously it is backward. It is not actually backwards on my sweatshirt. But what seen reflected from the mirror it appears backwards. The word "The" is on the right side of the sign, under my right hand. If I was, in fact, facing you, i.e., not reflected from a mirror, the word "The" would be on your left side and you would be able to correctly read the words "The Joy of Visual Perception.
Since I am not standing on my head, my head is up and it appears
so in the reflection from the mirror.
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