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प्रश्न
The magnifying power of an astronomical telescope in normal adjustment is 2.9 and the objective and the eyepiece are separated by a distance of 150 cm. Find the focal lengths of the two lenses.
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उत्तर
Given: D = 150 cm, m = 2.9
fo = ?
Since, `m = f_o/f_e`
D = `f_o + f_e`
`2.9 = f_o/f_e`
`f_o = f_e xx 2.9` .....(i)
`f_o + f_e = 150` cm
From equation (i),
`2.9 f_e + f_e = 150`
`3.9f_e = 150`
fe = 38.46 cm
fo = 2.9 × 38.46
fo = 111.54 cm
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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
- 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 the following three lenses. Which two lenses will you use as an eyepiece and as an objective to construct an astronomical telescope ? Give reason
| Lenses | Power (D) | Aperture (cm) |
| L1 | 3 | 8 |
| L2 | 6 | 1 |
| L3 | 10 | 1 |
With regard to an astronomical telescope of refracting type~ state how you will increase its:
1) magnifying power
2) resolving power
Write the two important factors considered to increase the magnifying power?
Write two important limitations of a refracting telescope over a reflecting-type telescope.
Define magnifying power of a telescope. Write its expression.
An astronomical telescope is to be designed to have a magnifying power of 50 in normal adjustment. If the length of the tube is 102 cm, find the powers of the objective and the eyepiece.
(i) What is meant by resolving power of a telescope?
(ii) State any one method of increasing the resolving power of an astronomical 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.
