I was learning some optics and then I wondered what would happen if some object was exactly in the focus of converging lens, more accurately, what would I see if looking from the other side?

EDIT: so there would be candle. The candle would be exactly at focus. The tip of the flame would be "sending" rays of light toward the lens. Parallel ray would hit the lens and then go right towards focus while vortex ray would go through the vortex of the lens unchanged but parallel to the first ray so there would be no place where the image would create right?

I mean, the light rays would be parallel and they would never form an image.. probably. Thanks in advance!


closed as off-topic by garyp, Bill N, Norbert Schuch, user36790, Gert Dec 24 '15 at 3:46

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  • $\begingroup$ You'll have to explain your set up better. $\endgroup$ – garyp Dec 23 '15 at 17:07
  • $\begingroup$ Set up is described. $\endgroup$ – Vojta Klimes Dec 23 '15 at 17:19
  • $\begingroup$ When you say "focus" do you mean "focal point?" If so, then any standard physics text will explain the geometrical rays. $\endgroup$ – Bill N Dec 23 '15 at 18:14
  • $\begingroup$ An ideal lens with an object in the focal point will produce an approximation of the Fourier transform of the object. This can and has been used for analog computing devices that calculate Fourier transforms to perform spatial and temporal filtering at the ns or even sub-ns time scale. $\endgroup$ – CuriousOne Dec 23 '15 at 20:17
  • $\begingroup$ @CuriousOne Ok, I will have to find out some stuff since I do not know what Fourier transform is. I will ask if I dont understand anything. $\endgroup$ – Vojta Klimes Dec 23 '15 at 21:18

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