diverge from a focus

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Senior Member

The light waves that compose a virtual image (in a hologram) seem to be diverging from an apparent focus or source. This is an illusion, for the virtual image of a hologram has no more extension in space than does the image in a mirror. The real image of a hologram is formed by light waves that are coming to a focus, and this is not an illusion.(Holographic Universe/Michael Talbot)

Does "diverge from a focus" mean that they "lose focus"?
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  • entangledbank

    Senior Member
    English - South-East England
    No, 'losing focus' means becoming blurry. Virtual images are well defined, and they may be completely in focus, but they do not exist at the point where they appear to exist. The light rays diverge (move apart from) a point, outwards to your eye. This is as opposed to real images, where the light rays converge to a point, and the image is actually there. If you put a camera at the point where a real image is focused, you get a picture of the thing. A virtual image can only be seen from where you are looking at it, not where it appears to be to you. A camera at your eye position will get it, but a camera at its apparent position on the other side of the lens (or whatever) won't. See any physics text for a better and no doubt more accurate explanation, but that's physics rather than English language. 'Virtual image' is not an everyday term in English; people who have studied optics will know it, but no-one else will.
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