Reflection Of Light In A Mirror: Lateral Inversion/Left-Right Reversal

Have you ever observed lateral inversion or seen your reflection in a still surface of a lake? Surely, you must have seen a mirror. Why can we see our reflection on some surfaces and not others? Reflection of light is refers to the change in the direction of light upon striking a surface. This change in direction occurs whenever light hits a surface, irrespective of the surface’s texture or nature. The difference here is that in a reflective surface such as the shiny spoons, plates and mirrors, the reflection is uniform throughout the surface leading to a crisp reflection. Mirrors are what we use most often to see our reflection. The reflection of light from a mirror seems pretty straight forward until you move. When you move, another characteristic of an image comes into the picture. If you move your left hand while standing in front of a mirror, your mirror image moves your right hand. If you shake your right foot, your mirror image moves its left foot. So a mirror reverses left and right but not top and bottom? Is the mirror doing this intentionally to play tricks with you? Let’s take a look at this.

Lateral Inversion: Left-Right Reversal

The left and right of a mirror image appear reversed (lateral inversion) because of how we perceive the mirror image.

We will start by analyzing the image that the mirror has formed. When you stand in front of a mirror, your reflection stares back at you. This reflection is oriented correctly, as your top is the top for the image in the mirror. Your head and feet are pointing in the same direction. The phenomenon where your left appears as the right and vice versa in a mirror is referred to as Lateral Inversion. A very similar thing happens if you write a word, say ‘MIRROR’ on a piece of paper and keep it in front of the mirror. Go ahead and write a word and place it in front of the mirror. Can you read what you have written on the paper from the image you see in the mirror? You will find that the word ‘MIRROR’ is reflected as ‘MIЯЯOЯ’. Take another word to see the effect more clearly, say ‘REVERSE’ which is reflected as ‘ЯƎVƎЯƧƎ’. How a mirror reverses the left-right only is very confusing. Well, here’s the answer.

The lateral inversion we experience is not caused by the mirror but by our perception of the mirror image. Let’s examine a mirror image. For the sake of explanation, let’s say that your left hand is towards the East, your right hand towards the West, your nose is pointing towards the north and the back of your head towards the south. Now, if you see the image carefully, you will notice that in the mirror image, your arms, nose and head are all aligned in the same directions, i.e. your left hand is still towards the East, right hand towards the West, your nose is pointing towards the north and so forth. What causes the lateral inversion is how we see it. Your brain, when it sees a mirror image, tries to make sense of it. Doing so imagines that another you have walked to the mirror and is standing in front of you from behind the mirror. So now, even though your arms are facing in the right directions, your nose, initially pointed towards the North, has gone to the back of the screen facing the opposite side now, i.e. the South. This means that a mirror does not reverse left and right, contrary to how we see mirror images. Instead, it reverses the front and back. Where your back should be, your face is, and your brain assumes this to be another person standing in front of you and assumes the left and right reversal, i.e. the lateral inversion.

If you look at a person’s shirt from the front, the letters do not appear reversed. Now if you view the same shirt from behind the shirt, the letters would appear reversed. This is exactly what happens in a mirror, the front is viewed as it would be from

This effect is also observed with letters. Since letters are two dimensional, the lateral inversion stands out more. If you read a word from the mirror, it is inverted front and back as well. If you write the laterally inverted word on a piece of paper and look at it from behind, it will seem normal to you, although it will still be reversed as it is a mirror image, the letters are recognizable now. The front-back reversal is what causes the lateral inversion that confuses us so.

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