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The phenomenon of image formation

  1. Dec 12, 2009 #1
    the main question/doubt that I have is about the possibility of image formation through parallel projection [I'll explain in detail what I mean by that]. To make myself clear, I will start with a different question and connect that to this.

    + Consider a small rectangular box of a length, say, one metre. On one end of the face I have kept a photographic plate[PP] with a proper mechanism to cover and uncover it. On the opposite face I have stuck a shiny reflective coin. The whole box is well light [some mechanism - but don't think a bulb will hanging down from the top in the middle of the box].
    ++Please don't bother about the other details as they are not relevant to what i am intending to convey. If its important, you will point it anyhow.​
    +Now, I will introduce a wall in between these two faces which has a lens [or a small hole - camera obscura]. Assume that the distances:that between the object & the lens and lens & screen [PP], focal length, etc. are all fine for the image to be formed on the PP.
    And if I remove the cover now, a proper image would have been formed, as expected.

    1)Q1:My question is - how should I interpret the process of formation of the image, say on the screen? That is, how should i describe the aetiology of image formation?
    1.1) The obvious answer is through ray diagram [geometric optics]. But that is not what I am asking.
    To describe that consider the step by step process of this phenomenon.
    1.2) the photons are being reflected by the coin. When these photons pass through the lens, they get refracted appropriately.
    Q1.1:Should I interpret light in this part as particle or wave?​
    1.3) After this I am totally confused. What exactly happens after this? How is that the refracted light rays [or particles] form the image – which is of the surface from which these rays came?
    1.4)Q1.2: How can the light after coming out of the lens, still have the information of the object it is getting reflected from, but in such a way that it is either magnified or diminished?
    1.5)Q1.3: Basically, what is an image?
    What exactly do we mean by the "rays" coming from the object gets focused to form the image?

    Also refer point (2.4) for this question.

    2. My second main question starts from the previous question [Q1.3].
    The "image" is present only when the rays are focused. Let me explain why I concluded so.
    2.1)In the previous set up of the box, assume that there is no wall in between. Now, if I open the cover of the PP, it will be exposed to the light present inside the box.
    The main point is it will not have the image of the coin even though it is present right in front of it. The reason [i think so] would be that the light from the coin would not have been focused on to the PP to form an image.
    ++This is what I think. Please do correct me if I am wrong. ​
    2.2) A simple example & an explanation that I can give is to just open a film roll. It will be exposed and will not have anything even though I am staring at it.
    2.3)There are two reasons that I could think of for this effect -
    ++The photons will react to the film's chemical substance immediately​
    ++No image is focused on to it in a controlled manner​
    Of course, both these reasons are over lapped. but the main reason would be the absence of a focused image, which will internally control the way the chemical substance has to react.
    2.4) You may suggest that the image formed on the film roll would be related to the energy of the photon [and various other parameters which i am not aware of] striking the film's surface.
    ++This being similar to the way an electronic photoreceptor works- depending on the energy levels of each pixel of it​
    But, it is not the chemical reaction or the picture formation that I am talking about. I am talking about the “image” – it is irrelevant if it forms on a plain screen or a photographic film. Again Q1.3 comes into picture.
    Is "image" a collection of photons coming from a body which is refracted by the lens - not changing their characteristics, but just the direction?
    2.5) Q2.1:Does this means that a collection of rays or photons coming from an object will NOT form an image on a screen if they are not focused on to it?
    2.6) now, the characteristic of the image formed would be that of the http://en.wikipedia.org/wiki/Perspective_%28graphical%29" [Broken].
    2.7) Q2.2: I cannot have the image formed of an object without a lens. This implies that I CANNOT have an image of that object with parallel projection. Am I correct?
    ++now, perspective projection would be parallel projection for certain configuration. See the details given below the right hand side image in this http://en.wikipedia.org/wiki/Graphical_projection#Overview"

    Please clarify my doubts or show where I am going wrong.
    Last edited by a moderator: May 4, 2017
  2. jcsd
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