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Brightness of real images from converging lens

  1. Sep 27, 2010 #1

    Have a question about images from a converging lens. I assume that the brightness of the (real) image projected on a screen depends upon the amount of light rays going through the lens - more rays -> brighter. So a larger lens should bring about a brighter image.

    Ok, now let's go the the extreme situation of making the converging lens smaller and smaller thereby making the brightness of the image dimmer and dimmer. Eventually only one ray passes through the lens which would be equivalent to having no lens at all.

    My question is, can you think of a real image being formed even when there is no lens but since the real image only contains one ray, it is completely dimmed and therefore unobservable?

    To think of in another way. Consider no lens. Consider the rays emanating from some point on an object. One of those rays goes to a point on the wall. We see no image though. However if we 'take' other rays coming from the object point, we can see an image (this is what the lens does, right?). So not seeing the image due to the one ray is really a matter of dimness.

    Any thoughts on this would be appreciated.
  2. jcsd
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