Q. No.In an astronomical telescope, the focal length of the objective lens is \(100\) cm and of the eyepiece is \(2\) cm. The magnifying power of the telescope for the normal eye is:
| 1. | \(50\) | 2. | \(10\) |
| 3. | \(100\) | 4. | \(\dfrac{1}{50}\) |
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The magnifying power of a telescope is \(9\). When it is adjusted for parallel rays the distance between the objective and eyepiece is \(20\) cm. The focal lengths of lenses are:
| 1. | \(10~\text{cm}, 10~\text{cm}\) | 2. | \(15~\text{cm}, 5~\text{cm}\) |
| 3. | \(18~\text{cm}, 2~\text{cm}\) | 4. | \(11~\text{cm}, 9~\text{cm}\) |
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To increase the magnifying power of a telescope:
| 1. | The focal length of the eyepiece should be increased. |
| 2. | The focal length of the objective should be increased. |
| 3. | The wavelength of light should be increased. |
| 4. | The aperture of the eyepiece should be increased. |
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An astronomical telescope has angular magnification of \(40\) in its normal adjustment. If focal length of eyepiece is \(5\) cm, the length of the telescope is:
1. \(190\) cm
2. \(200\) cm
3. \(205\) cm
4. \(210\) cm
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An astronomical telescope has angular magnification of \(20\) in its normal adjustment. Focal length of eyepiece is \(4\) cm. Distance between objective and eyepiece is:
| 1. | \(80\) cm | 2. | \(84\) cm |
| 3. | \(76\) cm | 4. | \(90\) cm |
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In normal adjustment, the angular magnification of an astronomical telescope is \(39\). If length of the tube is \(2\) m, then focal length of the objective and eyepiece are respectively:
| 1. | \(195~\text{cm}, 5~\text{cm}\) | 2. | \(190~\text{cm}, 10~\text{cm}\) |
| 3. | \(20~\text{cm}, 180~\text{cm}\) | 4. | \(10~\text{cm}, 190~\text{cm}\) |
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The minimum magnifying power of an astronomical telescope is \(40\). If the length of the telescope is \(205\) cm, then the focal length of its field lens is:
1. \(5\) cm
2. \(200\) cm
3. \(40\) cm
4. \(140\) cm
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| 1. | \(46.0\text{cm}\) | 2. | \(50.0\text{cm}\) |
| 3. | \(54.0\text{cm}\) | 4. | \(37.3\text{cm}\) |
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1. \(\frac{L}{l}+1\)
2. \(\frac{L}{l}-1\)
3. \(\frac{L+1}{l-1}\)
4. \(\frac{L}{l}\)
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| 1. | \(10\) cm and \(80\) cm |
| 2. | \(85\) cm and \(5\) cm |
| 3. | \(70\) cm and \(20\) cm |
| 4. | \(5\) cm and \(85\) cm |
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