Magnification
An object can be made to appear â€˜bigâ€™ or â€˜magnifiedâ€™ by increasing the visual angle. Magnification or magnifying power (m) is the ratio of the visual angle while looking through the instrument to that with the naked eye.
Ray diagrams of the above-mentioned optical instruments are shown in Figures .
Ray Diagram of Simple Microscope
Magnification , where D is the least distance of distinct vision.
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Figure 9.28 Ray Diagram of Compound Microscope
Magnification , where L is the separation between the objective and the eyepiece D is
the least distance of distinct vision, f_{o} is the focal length of objective and f_{e} is the focal length of eyepiece.
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Figure 9.29 Ray Diagram of an Astronomical Telescope
Magnification m = , where f_{o} is the focal length of the objective and f_{e} is the focal length of the eyepiece.
Differences Between Compound Microscope and Astronomical Telescope
Compound Microscope |
Astronomical Telescope |
â€¢ Objective of shorter focal length â€¢ Eyepiece of larger focal length â€¢ Object, outside f_{0} (principal focus of objective) â€¢ Used for studying microorganisms (to enlarge very small objects) |
â€¢ Objective of larger focal length â€¢ Eyepiece of shorter focal length â€¢ Object at infinity â€¢ Used for astronomical purposes (to view distant objects) |
A pair of telescopes, which is designed to be used together is called a binocular.