What is the cause of lateral of lateral inversion? Why is it that the image is flipped only horizontally but not vertically?
What is the cause of lateral of lateral inversion? Why is it that the image is flipped only horizontally but not vertically?
Lateral inversion in a plane (flat) mirror means the apparent reversal of left and right in the mirror image compared with the object. Lateral means "sideways".
However, the mirror image is really a reversal of the the object in the direction perpendicular to the mirror's surface (more correctly called the direction "normal" to the mirror plane). In a plane mirror, each point on the image is as far behind the mirror plane as the corresponding point on the object is in front. That's all there is to it in terms of the physics, the "geometrical optics". However, we usually notice a left-right reversal in the image. We need to consider the "psychology of perception" to explain that.
What follows is mainly a discussion of the psychology involved here. I would like people to take the time to read it all, but you may like to just skim through to find anything of interest. I realise it will be too long (don't read) for many people.
Consider your own mirror image. You don't easily perceive your front and back as reversed even though that is what happens when you face a mirror. In fact, the mirror seems to reverse your left and right. Left and right are usually defined by where your front and top are and people tend to take their image’s front as the starting point for defining their image’s left and right.
If you move your right hand, the "mirror hand" that moves is still on your right side. There's no reversal in that sense. However, your right hand is perceived as the left hand of your image. The perceived reversal of intrinsic left and right is "lateral inversion". We often perceive these left-right mirror reversals. So, that's why mirror reversals are called "lateral inversion", even though that's not usually what the mirror does directly.
Left and right are the only directions which are described relative to the observer. Up and down (and north, south etc) are independent of whichever way you're facing. When you look in the mirror, up, down, east and west are still in the same place. But you read printed text from left to right - not east to west - hence the problem with 'mirror writing'.
Lateral inversion in a plane (flat) mirror means the apparent reversal of left and right in the mirror image compared with the object. Lateral means "sideways".
However, the mirror image is really a reversal of the the object in the direction perpendicular to the mirror's surface (more correctly called the direction "normal" to the mirror plane). In a plane mirror, each point on the image is as far behind the mirror plane as the corresponding point on the object is in front. That's all there is to it in terms of the physics, the "geometrical optics". However, we usually notice a left-right reversal in the image. We need to consider the "psychology of perception" to explain that.
What follows is mainly a discussion of the psychology involved here. I would like people to take the time to read it all, but you may like to just skim through to find anything of interest. I realise it will be too long (don't read) for many people.
Consider your own mirror image. You don't easily perceive your front and back as reversed even though that is what happens when you face a mirror. In fact, the mirror seems to reverse your left and right. Left and right are usually defined by where your front and top are and people tend to take their image’s front as the starting point for defining their image’s left and right.
If you move your right hand, the "mirror hand" that moves is still on your right side. There's no reversal in that sense. However, your right hand is perceived as the left hand of your image. The perceived reversal of intrinsic left and right is "lateral inversion". We often perceive these left-right mirror reversals. So, that's why mirror reversals are called "lateral inversion", even though that's not usually what the mirror does directly.
Left and right are the only directions which are described relative to the observer. Up and down (and north, south etc) are independent of whichever way you're facing. When you look in the mirror, up, down, east and west are still in the same place. But you read printed text from left to right - not east to west - hence the problem with 'mirror writing'.
