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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 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
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| L1 | 3 | 8 |
| L2 | 6 | 1 |
| L3 | 10 | 1 |
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