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प्रश्न
Draw a labeled ray diagram to obtain the real image formed by an astronomical telescope in normal adjustment position. Define its magnifying power.
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उत्तर
In normal adjustment, the final image is formed at infinity.
Magnifying power or angular magnification of astronomical telescope: It is defined as the ratio of the angle subtended at the eye by the final image to the angle subtended at the eye, by the object directly, when the final image and the object, both are at infinity.
Angular magnification,`M=beta/alpha`
β and α are very small.
`:.beta~~tan beta`
`alpha~~tanalpha`
`=>M=tanbeta/tanalpha`
I is the image formed by the objective. f0 and fe are the focal lengths of the objective and eyepiece, respectively.
Here,
`tanalpha=I/f_0`
`tan beta=I/-f_e`
(Distance of the image from the eyepiece is taken as negative.)
`:.M=((-I)/f_e)/(I/f_0)`
|
`M=(-f_0)/f_e` |
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संबंधित प्रश्न
- A giant refracting telescope at an observatory has an objective lens of focal length 15 m. If an eyepiece of focal length 1.0 cm is used, what is the angular magnification of the telescope?
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1) magnifying power
2) resolving power
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A giant refracting telescope at an observatory has an objective lens of focal length 15 m. If an eyepiece lens of focal length 1.0 cm is used, find the angular magnification of the telescope. If this telescope is used to view the moon, what is the diameter of the image of the moon formed by the objective lens? The diameter of the moon is 3.42 × 106 m and the radius of the lunar orbit is 3.8 × 108 m.
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 small telescope has an objective lens of focal length 140 cm and an eyepiece of focal length 5.0 cm. Find the magnifying power of the telescope for viewing distant objects when
- the telescope is in normal adjustment,
- the final image is formed at the least distance of distinct vision.
