Stand in front of mirror facing it.Why the mirror appears to reverse left and right, but not up and down?

Question

Imagine you are standing in front of a mirror, facing it. Raise your left hand. Raise your right hand. Look at your reflection. When you raise your left hand your reflection raises what appears to be his right hand. But when you tilt your head up, your reflection does too, and does not appear to tilt his/her head down. Why is it that the mirror appears to reverse left and right, but not up and down?

Answer 1

Because the mirror is reflecting the point directly in-front of it. Your left hand is directly in-front of the right side of the mirror (from the mirror's perspective), your head is directly in-front of the upper part of the mirror, etc.

Answer 2

Your perspective on the inversion is incorrect: a mirror reverses the image neither up/down nor left/right. Consider the following;

Place a mirror flat on the ground, and place a compass on it, to indicate north, south, east, and west. Lean over the mirror, looking straight down, into the reflection. Assuming that your head is north (by compass bearing), your right hand is east, and your left hand is west. If you apply these (relative) absolute directions, rather than your relative right/left perspectives, you can see that the reflection of your head is also north, the reflection of your right hand is also east, and the reflection of your left hand is also west.

In fact, the only inversion occurs perpendicular to the plane of the mirror. If you were to look into a mirror which was flat on the ground, the reflection would be reversed along the up/down axis, with your relative front/back relationship appearing reversed.

Answer 3

In a plane mirror, the image is formed so that the distance of the image from the mirror and the distance of the object from the mirror are equal.

If you turn your head up, the distance of the head from the mirror increases; so the distance of the image (head) also increases.

If you lean to the front, the distance decreases. Hence the image also leans to ward the mirror, so as to decrease the distance.

Objects and their images are at the same distance from the mirror.

The next property of the image in a plane mirror is as follows.

A line drawn from any point on the object to a similar point of the image will be perpendicular to the plane of the mirror.

If you draw a line from the thumb of your left palm to the similar palm of the image (if we personify the image to be a real person, then it will be the right thumb), the line will be perpendicular to the mirror.

Keeping in mind these two properties of plane mirror, if you analyze the image, every thing will be clear.

Instead of the image, if there were a real person, as you lift your left hand, he will also lift his left hand. But the image raises its ‘right hand’. This is because the images of the objects which are left side to you are also on the left side in the mirror.

Answer 4

First two answers are correct lateral inversion is a not exactly what mirror does.Though you find that misleading word everywhere it really doesn't capture what mirror is actually doing.There is basic flaw in imagining yourselevs in the position of the person in reflection.Put the mirror on the ground and look at the sky or ceiling you don't find any inversion.What mirror does in fact is a full 180 turn.Move your hand towards the mirror and it seems to come towards you in the reflection.That is what mirror does inverts anything perpendicular to it's plane by 180.
Even I stuggled with lateral inversion physics text books so don't worry a lot of folks are confused.But on the whole the term is OK.It gives you a general idea but doesn't tells you why.

Answer 5

There is no left and right, only top and bottom. Left and right was a concept created by the Greek, Acromedius in 878 BC after his cousin, Lamont, created the mirror and discovered reflection. This was a strange concept to the Greeks and most likely the Albanians too, and they needed some way of explaining it to the general masses, so they invented Left and Right and we still use the concept today.

Answer 6

"Angle of reflection= angle of incidence". Think on that while you're going to build a "true vue" mirror.

Take 2 pieces of mirror, approximately 5" wide and 6" tall.
Glue them (I strongly encourage you to mount them to either plywood or something strong so it doesn't break using just the glass itself) into an "L" shape @ 90 degrees.

If you look into this mirror correctly, the left side will see the right side, and the right will see the left. Play with this a bit- You'll see what I'm talking about- good luck

Answer 7

It does. Lay it on the floor directly in front of you, then look at the image of the wall opposite from you. You will see than just like the mountains reflected in a lake are reversed and also upside down, so is the image you are looking at.

Answer 8

A mirror reflects light. The light it reflects is simply bounced off from the source (your body) to the observer (your eyes). Light from your left side would come off the mirror's left, side, which would seem to be its right side. However, light from the top of your head would also come off the mirror's 'top', which the human eye interprets as coming from the top.

Answer 9

Stand at a point and keep your mirror (6 ft height X 3 ft width) on your side so that you and your mirror face in one direction. Rotate your mirror 180 degree along the y-axis (vertical axis). Now you can face the mirror and can see your image in the mirror (as you mentioned in your question). This is because, the mirror is rotated 180 degree along only one axis (ie., y-axis only). After this stage, you rotate 180 degree your mirror about its upper horizontal frame (ie., about x-axis). Now the mirror is above your head, facing the direction, you face. Now you cannot see your image in the mirror. But, somebody else, who is standing before you can see your inverted image in the mirror. Thus, rotation of 180 degree each in x and y axes will give the image as you expected but not by single rotation of mirror in any one of these axes.

Answer 10

left-right is due to lateral inversion.
Top-down does not happen because the image formed by a plane mirror is virtual, erect, same size as the object and the image is far behind the mirror, as the object is infront of it.
Please refer any Physics textbook for explaination.