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  • Category: Miscellaneous
    Points:5

    Why image in a plane mirror seems swapped between left and right!

    When we view ourselves in a plane mirror then we see our image. We all use plane mirrors in our houses for dressing up or anything of that sort. It is an important item in our household.
    If we observe the image we would find a strange thing that if we are holding something in our right hand the image would appear as holding it in our left hand. If we are wearing a wristwatch in our left hand the image would appear wearing it in the right hand. So, everything seems shifted from left to right and right to left.
    What could be the reason for that? How can we explain that in simple terms? Members may try to explain this phenomenon.
  • #779513

    Points:5
    Our body is opaque and will not reflect any light. Hence when we stand before a mirror there should be a shadow. A mirror has a highly polished surface and reflects the light. Therefore we will not see our shadow but we will see our picture as our eyes see the reflected light. Left and right are only directions and they are relative to the observer. Stand looking east and then turn west, your right side will become your left side.
    A mirror will not reverse left and right. But it reverses back and front. Your front will be facing east but your mirror image in the mirror will be facing west. It was reversed front to back. There will be no rotation at all. If you are standing opposite to a mirror, it reverses front and back. If you stand in a sideway of a mirror then your image will not change your left and right.
    This phenomenon is known as lateral inversion, I read somewhere. Lateral inversion is nothing but the interchange of the left and right sides in the image of an object in a plane mirror.
    drrao
    always confident

  • #779520

    Points:2
    I have also read about this in some science articles and there are different ways this phenomenon is explained. However you have explained it in a unique way under the theory of lateral inversion.
    Let us wait for some more responses in the matter and get other viewpoints before making some final views in the topic.
    Knowledge is power.

  • #779544

    Points:4
    As I recall my school days and science classes, the light ray gets reflected from a plane mirror and it appears to us coming from a point inside that mirror. So, what we are seeing is the virtual image and every point of our body is straight at the same point inside the mirror which juxtaposes the image appearing left and right swapped.
    I remember during our childhood there was a special wax type of crayon pencil which when we rubbed on a newspaper or magazine figure and pressed it against a blank paper the figure was printed on the blank paper. That was also a left to right and right to left swapped figure because each point on the original figure corresponded directly on the image creating lateral inversion.
    Thoughts exchanged is knowledge gained.

  • #779558

    Points:5
    To summarise, whether we call it lateral inversion or left to right and right to left swapping, the point is that the light rays travel in a straight line and image of each and every point of our body is formed straight inside the mirror and that line is making a angle of 90 degrees to the mirror (technically called perpendicular). This creates a virtual image in the plane mirror that appears to be situated deep in the mirror by same distance as our body is from the mirror.
    If on our T-shirt there is something written like say 'India' then we would see it in the image in reverse and all the letters will also be laterally inverted.
    Have you ever seen the word 'Ambulance' written in a laterally inverted way so that a driver driving a vehicle ahead of the ambulance sees it correctly in his plane mirror and gives way to it to go ahead?
    Knowledge is power.

  • #779566

      

    Points:3
    I too have noticed this inversion in some mirrors. After reading this thread I stood before the mirror, just to clear my doubt, and observed that the image was exactly the same as the way I was standing. But yes, when I held a printed paper against the mirror, the letters were upside down and reversed. Now, I am more confused. Can our experts/ those interested in Physics please get deeper into this point and explain?
    'Educating the mind without educating the heart is no education at all'.
    -Aristotle

  • #779573

    Points:5
    Saji, in Physics this phenomenon is called lateral inversion in which the whole left part appears as right and whole right part appears as left of the image.

    To understand it in simple terms we have to understand the reflection of light from a plane mirror. Plane mirror makes the laterally inverted image of any object and the image is formed inside the mirror at the same depth as the object is away from the mirror.

    Now this image that we see is virtual. We see the image sitting there inside the mirror. From our daily perception we will take that image facing us and accordingly consider his right side and left side. Further, his right side is nothing but the image of our left side and his left side is nothing but image of our right side. So, the virtual person sitting inside the mirror seems to us laterally inverted.

    Please note that this inversion is only lateral. There is no upside down. Many students of Physics get confused between 'lateral inversion' and 'upside down'. They are totally different effects.

    When we are standing, our body is symmetrical about a vertical axis going centrally from top to bottom of our body and at times we may not notice the inversion in the plane mirror in front of us but as soon as we wear a wrist-watch on our left hand we would see the virtual 'me' wearing it in his right hand. The pocket on the left side of my shirt would also appear shifted to right side of the virtual image. If a lady is standing in my place and having a nose pin on the left side of her nose then the virtual lady will be having it in her right side of nose. So, basically it is the perception of right and left in our minds that we are attributing to that virtual image and feeling the lateral inversion.

    I remember, during my student life I saw one roadside magician/artist using a soft wax type chemical stick that he applied on a photograph in a newspaper and placed a blank white paper on it and pressed it hard and rubbed for a while and the photo image got transferred on the blank sheet. The photo was not very sharp like today's printers but it impressed the audience and many people bought that wax candle from him and he was selling that by roaming from one place to other. If we see that print then it is just like the virtual image that we see in a plane mirror. This point to point transfer of photo to the print is the best analogy that I can give to explain the point to point formation of virtual image by a plane mirror.

    Hope this explanation helps all the readers to understand the phenomenon more clearly.
    Knowledge is power.

  • #779581

    Points:4
    This phenomenon will be observed when you stand exactly opposite to the mirror. But if you are standing sideways this phenomenon will not be noticed. There are many views and theories explained by different people regarding this phenomenon called ' Lateral Inversion '. The main point here is our body is opaque and will not reflect any light and the mirror reflects the entire light. So we can see our image there in the mirror. We see the shadow of our body will not reflect any light in the night.
    drrao
    always confident

  • #779584

    Points:5
    Dr Rao, you have explained it in slightly different way but I will like to make that more clear.

    Let us go into the fundamentals of answering the question - how we perceive an object?
    The answer is that when light (sunlight or electric light or burning fire light in the night or candle light or a kerosene lamp) falls on any object then a part of the light can pass through it as well as a part can be absorbed by it and finally a part can be reflected by it. All of the three possibilities are there as well as a combination of them. During that the light breaks up in its colour components and depending upon which colour it reflects and which it absorbs, we perceive the colour of the object. For example a wall painted with red paint will reflect red light that reaches our eyes and we say that it is red. Our eyes can nicely distinguish these colours. In the dark there is no light and we do not see anything. This is just a background material for those readers who do not know how we perceive the objects in light with our eyes.

    Coming to our body in the light, the body is also reflecting some light and that light is falling on the plane mirror and almost all the light is reflecting creating a clear virtual picture appearing inside the mirror. Rest of the matter I have tried to explain in my earlier response #779573.

    Remark:
    Regarding standing sideways as one of the sides would be obscured and out of sight we would not see the inversion but if we move our left or right hand to and fro we will see the virtual image moving it's right or left hand! That is inversion only.
    Knowledge is power.

  • #779592

      

    Points:4
    Umesh, got your point at # 779573 and thanks, to Dr Rao too, for the explanation. But is it limited to plane mirrors only? I think the same would be applicable to images that are reflected on any surface in which images are visible. For example, I just checked out by looking at my image in the floor tile and the result was the same. So, is it just a perception or is there more to lateral inversion?
    I am just trying to force experts here to explore further since this is a scientific topic and people reading the thread may stand benefited if we are able to throw more light, to the extent we can, on the subject.
    'Educating the mind without educating the heart is no education at all'.
    -Aristotle

  • #779598

    Points:4
    Saji, a polished tile or granite or any polished plane surface will behave in the same manner as that of a plane mirror. Only difference is as they reflect less light as compared to a plane mirror the image would not be so clear. Even a still water plane surface in a pond or tank will show our reflection like that only.
    The main point in perceiving this inversion is that we are treating the virtual image as a real person standing there and seeing towards us and when we salute him with our right hand he does it with his left hand!
    His left hand is nothing but image of our right hand. Our image is mimicking us albeit with lateral inversion.
    Knowledge is power.

  • #779602

    Points:2
    This thread has given some good points and details about the reflection of light by a plane mirror and formation of the virtual image having lateral inversion. Thanks to the expert contributors.
    Thoughts exchanged is knowledge gained.


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