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Why does our reflection in a mirror look backwards?

A mirror does not swap left and right — it actually swaps front and back, but we perceive it as left-right.

When you look in a mirror and lift your right hand, your reflection seems to lift its left hand. But the mirror does not really mix up left and right. A mirror sends light straight back the way it came. That is why the side facing forward in the picture ends up facing backward.

Here is a way to picture it. Imagine you are lying on the floor and the mirror is right above you. Then the mirror seems to swap your head and your feet, not your left and right, because the up-down direction gets flipped instead. It only looks like left and right are swapped because that is how we stand when we face a mirror.

In truth, the mirror is not flipping anything at all. Rays of light hit the mirror and bounce straight back at the same angle. Because your body is symmetrical — your right side and left side look a lot alike — your brain always reads this flip as 'left-right', even though that is not really what is happening.

Quick facts

A mirror swaps front and back, not left and right.
When light hits a mirror, it bounces back at the same angle it arrived.
This is called reflection.
Because the human body is left-right symmetrical, our brain reads the flip that way.
Calm water can reflect a picture just like a mirror.
The first mirrors were made of polished stone and metal.

Check what you remember

3 questions — all of them come from the quick facts above. There is no score and no wrong turn.

1. What does a mirror really flip?

2. What happens when light hits a mirror?

3. What were the first mirrors made of?

Where this comes from

1 tr.wikipedia.org 80/100
Mirror - Wikipedia
A reliable encyclopedia page about how mirrors work and their history.
2 nasa.gov 55/100
NASA
You can find simple, fun facts and pictures about light and space.

💡

How Light Bounces Back

When light hits a flat surface, it bounces back at the same angle it arrived. This is called reflection. A mirror is such a smooth surface that it reflects a clear, sharp picture.

🧍

Your Symmetrical Body

The human body has a right side and a left side that look very alike. That is why we always think the mirror swaps left and right, when really it swaps front and back.

🪞

The Invention of Mirrors

The first mirrors were made of polished stone and metal. Glass mirrors were made centuries later. Mirrors today have a thin layer of silver or aluminium on the back.

💧

Water Can Be a Mirror Too

You can see yourself in a calm pond because the water's surface reflects light too. Long ago, people may have first seen their own reflection in water.

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