Chapter 73 of 2364 min read
Optical instruments: microscope and telescope
Why this is asked: A microscope's magnifying power rises as its lenses' focal lengths get shorter, but a telescope's, fo/fe, rises as the OBJECTIVE's focal length gets longer — opposite dependence, which is why microscope objectives are tiny and telescope objectives are built as large as possible.
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- •A microscope has an objective of focal length 2 cm, an eyepiece of focal length 4 cm and a tube length of 40 cm. If the distance of distinct vision of the eye is 25 cm, the magnification of the microscope is:
- •A small telescope has an objective of focal length 140 cm and an eyepiece of focal length 5.0 cm. The magnifying power of the telescope for viewing a distant object is:
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