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Suppose there is a compound microscope consisting of two convex lenses i.e objective of shorter focal length and eyepiece of longer. For normal adjustment intermediate image is formed with in the focal length of eyepiece and it magnifies it to get the final image at near point. My question is why don't we use compound microscope in such an adjustment that first image is formed at the focal length of eyepiece and consequently forming final image at infinite ( as eyepiece of a telescope do ) ? Please someone tell me what are the drawbacks of doing so?

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  • $\begingroup$ The depth of field is very narrow so effectively there is no "infinity" focal length like there is for a telescope. $\endgroup$ – MaxW Jan 28 '17 at 7:13
  • $\begingroup$ Although the magnification is reduced the final image can be formed at infinity so that when the final image is viewed the eye is relaxed. $\endgroup$ – Farcher Jan 28 '17 at 7:43
  • $\begingroup$ @Farcher If final image is at infinity for telescope, does it means that it appears to form at about 100 meter from eye? Because if final image literally forms at infinite distance from eye, it will be of infinite size. Am I right? $\endgroup$ – rock Jan 28 '17 at 9:25
  • $\begingroup$ Your perception as to the size of an image is dictated by the angle the image subtends at the eye. physics.stackexchange.com/a/290100/104696 $\endgroup$ – Farcher Jan 28 '17 at 9:30

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