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Q. No.Why are lenses of different focal lengths used as the objective and eyepiece in an astronomical telescope?
1. To increase magnification.
2. To increase the focal length of the telescope.
3. To increase the amount of light captured.
4. To increase spherical aberration.
1. To increase magnification.
2. To increase the focal length of the telescope.
3. To increase the amount of light captured.
4. To increase spherical aberration.
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A refracting telescope is adjusted for normal vision, with a distance of \(30~\text{cm}\) between its objective and eyepiece. If its angular magnification is \(2,\) what is the focal length of the objective lens?
1. \(20\) cm
2. \(30\) cm
3. \(10\) cm
4. \(15\) cm
1. \(20\) cm
2. \(30\) cm
3. \(10\) cm
4. \(15\) cm
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A telescope has a tube length of \(60 ~\text{cm}\) and a magnifying power of \(5 .\) What is the focal length of its eyepiece?
| 1. | \(40 ~\text{cm}\) | 2. | \(10 ~\text{cm}\) |
| 3. | \(20 ~\text{cm}\) | 4. | \(30 ~\text{cm}\) |
Subtopic: Telescope |
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A compound microscope consists of an objective lens of focal length \(1~\text{cm}\) and an eye piece of focal length \(5~\text{cm}\) with a separation of \(10~\text{cm}\). The distance between an object and the objective lens, at which the strain on the eye is minimum is \(\frac{n}{40}~\text{cm}\). The value of \(n\) is:
1. \(100\)
2. \(50\)
3. \(25\)
4. \(10\)
Subtopic: Telescope |
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Two stars are \(10\) light years away from the Earth. They are seen through a telescope of objective diameter \(30~\text{cm.}\) The wavelength of light \(600~\text{nm}.\) To see the stars just resolved by the telescope, the minimum distance between them should be (\(1\) light year \(= 9.46 × 10^{15}~\text{m}\) ) the order of:
1. \(10^8~\text{km}\)
2. \(10^6~\text{km}\)
3. \(10^{11}~\text{km}\)
4. \(10^{10}~\text{km}\)
1. \(10^8~\text{km}\)
2. \(10^6~\text{km}\)
3. \(10^{11}~\text{km}\)
4. \(10^{10}~\text{km}\)
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An observer looks at a distant tree of height \(10~\text{m}\) with a telescope of magnifying power of \(20\). To the observer, the tree appears:
| 1. | \(10\) times taller |
| 2. | \(10\) times nearer |
| 3. | \(20\) times taller |
| 4. | \(20\) times nearer |
Subtopic: Telescope |
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A telescope has an objective lens of focal length \(150~\text{cm}\) and an eyepiece of focal length \(5~\text{cm}.\) If a \(50~\text{m}\) tall tower at a distance of \(1~\text{km}\) is observed through this telescope in a normal setting, the angle formed by the image of the tower is \(\theta,\) and \(\theta\) is close to:
1. \(15^\circ\)
2. \(60^\circ\)
3. \(30^\circ\)
4. \(18^\circ\)
1. \(15^\circ\)
2. \(60^\circ\)
3. \(30^\circ\)
4. \(18^\circ\)
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