Question

Find the distance between the objective and eyepiece lenses in the telescope in the above problem needed to produce a final image very far from the observer, where vision is most relaxed. Note that a telescope is normally used to view very distant objects.

$d \lt 102.5\textrm{ cm}$

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Video Transcript

This is College Physics Answers with Shaun Dychko. We have a telescope that has an objective focal length of 100 centimeters and an eyepiece focal length of 2.50 centimeters and because these focal lengths are both positive, we know the type of telescope we are working with is one that has two convex lenses— the concave lens would require a negative focal length. So we have two convex lenses and the question is what is the distance between the objective lens and the eyepiece lens? So in this scenario, we know that the image produced by the objective has to be at this position between the focal point of the eyepiece and the eyepiece lens and we are trying to find this total distance between the objective and the eyepiece and so we know that this total distance has to be something less than the focal length of the objective plus the focal length of the eyepiece and so we know that this distance has to be somewhat less than 100 centimeters plus 2.50 centimeters or something less than 102.5 centimeters.