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प्रश्न
Describe briefly the two main limitations and explain how far these can be minimized in a reflecting telescope ?
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उत्तर
Two limitations of refractive telescope are:
1. The lens used in refractive telescope are expensive.
2. The lens used for making refracting telescope have chromatic aberration and distortions.
They can be minimised by using reflecting type telescope, which use concave mirror rather than a lens for the objective. Reflecting type telescope has the following advantages:
1. They are free from chromatic aberration as mirror is used instead of lens.
2. There is no problem for mechanical support because weight of mirror is much less than the weight of the lens. It can be supported easily.
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संबंधित प्रश्न
Draw a labeled ray diagram to obtain the real image formed by an astronomical telescope in normal adjustment position. Define its magnifying power.
A small telescope has an objective lens of focal length 140 cm and an eyepiece of focal length 5.0 cm. What is the magnifying power of the telescope for viewing distant objects when
- the telescope is in normal adjustment (i.e., when the final image is at infinity)?
- the final image is formed at the least distance of distinct vision (25 cm)?
Why should the objective of a telescope have large focal length and large aperture? Justify your answer.
You are given three lenses of power 0.5 D, 4 D, and 10 D to design a telescope.
1) Which lenses should be used as objective and eyepiece? Justify your answer.
2) Why is the aperture of the objective preferred to be large?
Draw a ray diagram showing the image formation of a distant object by a refracting telescope ?
Draw a labelled ray diagram of an astronomical telescope to show the image formation of a distant object. Write the main considerations required in selecting the objective and eyepiece lenses in order to have large magnifying power and high resolution of the telescope.
The eyepiece of an astronomical telescope has a focal length of 10 cm. The telescope is focussed for normal vision of distant objects when the tube length is 1.0. m. Find the focal length of the objective and the magnifying power of the telescope.
A Galilean telescope is 27 cm long when focussed to form an image at infinity. If the objective has a focal length of 30 cm, what is the focal length of the eyepiece?
Draw a labelled ray diagram showing the formation of an image by a refracting telescope when the final image lies at infinity.
Draw a ray diagram of a refracting astronomical telescope when final image is formed at infinity. Also write the expression for its angular magnification (magnifying power).
