Aug 18, 2023

Mirrors Don’t Really Flip Things Left To Right

Back in April, a Tiktok trend about mirrors had people spooked, thinking that these silvery contraptions might have the somewhat magical ability to see behind obstructions. The reality of it was not magic but science – specifically, optics, the set of rules that we have worked out to explain how mirrors and lenses work.

Based on the feedback from that video, it seems that there is a specific misconception that lingers: The idea that mirrors flip things from left to right. Usual examples are done by holding a book, a newspaper, or any other piece of writing to the mirror, and seeing the text reversed back.

We are talking about flat mirrors here. Things get a bit more complex when we talk about concave or convex mirrors, but the principles are the same. The alleged "flip" from left to right or right to left is an illusion, our brain jumping to the wrong conclusion. We have prepared a video to prove just that.

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The experimental setup is simple. Find something around that is directional. Anything that has a clear front and rear would work. Hold it in your hand with the front pointing to your right while in front of the mirror. Where is the object pointing in the mirror? That’s right – in the same direction.

If flat mirrors were truly flipping things left to right, we should be wondering why they are not flipping up to down. The truth is, they are not changing in any specific direction. Mirrors actually create an inside-out version of our world.

If you think of a glove specific to the left hand, it won’t fit on the right. But if you can turn it inside out, it would. That is what the laws of optics do when it comes to flat mirrors.

If you look at an object, you can imagine light as moving in straight lines between your eyes and the object. When light encounters a mirror, it reflects depending on the angle at which it hits the mirror. That’s how it can see behind the paper. But looking straight at the mirror is like looking at a perfect mask of you that has been flipped inside out. The right-hand side of the mask needs to be facing the right-hand side of your body.

You might wonder why text is flipped, and the reason is similar. By trying to look at the text in the mirror, we have flipped the page. If we can see through the page by writing with a marker on a thin sheet, we would see the writing in the same way, both through the page and in the mirror.

For something so common, mirrors are really weird contraptions that have some pretty hardcore physics underlying their incredible properties.

All “explainer” articles are confirmed by fact checkers to be correct at time of publishing. Text, images, and links may be edited, removed, or added to at a later date to keep information current.