Why Do Mirrors Flip Right-Left but Not Up and Down?

Maybe some of you have thought that the mirror is like a portal to another world, more precisely the world of upside down. Mirrors are amazing since they were discovered centuries ago.

However, when we look in the mirror we see our reflection is reversed. In the mirror, the reflection of our right hand becomes the left hand while the left hand becomes the right hand. Why is that possible? How can a mirror swap right and left but can’t swap up and down?

What’s Flipped by a Mirror?

Actually the mirror does not reverse anything, whether it’s up-down or right-left. Take a look at the illustration below.

We can see in the illustration above on the arrows and shadows in the mirror. that the upward direction is still up, the downward direction is still downward, the left direction is still left, and the right direction is still right. Only the front and back of the mirror are reversed, as in the following illustration.

If the object moves into the mirror, then the object’s shadow will move out of the mirror. This happens because of the nature of the mirror itself, which is reflecting. That is, the light that initially leads toward the mirror, after bouncing the light will reverse direction away from the mirror.


If the Mirror Does Not Turn Right and Left, Why Can Writing Be Reversed?

We can try to write something on a transparent object and then we see the results in front of the mirror.

Look carefully at the illustration above. When the real writing can be read, it means it’s not reversed, so without changing the conditions, the writing on the mirror will also be able to read. Conversely, when the writing on the mirror is reversed, the actual writing will also be reversed. Things like this can only be seen in transparent objects.

Next is to use non-transparent objects. When we see the writing—for example on clothes—upside down, it’s because, in fact, the writing does not lead to us, but instead leads to the mirror. In other words, as long as the original text does not lead to us, then the writing will be reversed.

What turns things flipped is because we flip them. Initially, the objects and writing facing us were not reversed. However, when we want to see it in the mirror, we always turn it facing the mirror so that the writing or the object is reversed.

So why only right and left? Well, it just depends on how we rotate the object/writing into the mirror earlier. Generally, we rotate right and left, like when we turn around. But actually we can also spin it up and down, even though this method is not common.

Conclusion

The mirror does not flip left or right up and down, but only flipped front and back. The answer to why is our reflection reversed it is because we turned it over in the real world. If we see objects/writings in the real world are not reversed, then without changing the situation, writing in the mirror world will not be reversed.

Source and Reference:

  1. Why Do Mirrors Flip Left & Right (but not up & down)? – minutephysics

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