Which should be shorter for the same amount of magnification, a telescope with two converging lenses, or one with a converging lens and a diverging lens?
In Galilean telescope (one converging one diverging lens), it is possible to have a telescopic length lesser than the fo (focal length of objective lens). The net length would be around the difference of focal lengths of the two lenses.
For a Keplerian telescope (two converging lenses), it is not possible to have telescopic length lesser than the fo (focal length of objective lens). The net length would be about the sum of the focal lengths of the two lenses.
Thus, for the same amount of magnification a telescope with a converging lens and a diverging lens would be shorter than that of a telescope with two converging lenses.
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