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Question
Discuss about astronomical telescope.
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Solution
- An astronomical telescope is used to get the magnification of distant astronomical objects like stars, planets, moon, etc. the image formed by an astronomical telescope will be inverted.
- It has an objective of long focal length and a much larger aperture than the eyepiece.
- Light from a distant object enters the objective and a real image is formed in the tube at its second focal point.
- The eyepiece magnifies this image producing a final inverted image.
Astronomical telescope - The magnification m is the ratio of the angle β subtended at the eye by the final image to the angle ∞ which the object subtends at the lens or the eye.
m = `β/α`
From the diagram,
m = `("h"//"f"_"e")/("h"//"f"_0)`
m = `"f"_0/"f"_"e"`
The length of the telescope is approximate, L = f0 +fe
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