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. $\frac{1}{50}$

Subtopic: Â Telescope |
Â 89%
From NCERT
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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 cm, 10 cm

2. 15 cm, 5 cm

3. 18 cm, 2 cm

4. 11 cm, 9 cm

Subtopic: Â Telescope |
Â 85%
From NCERT
AIPMT - 2012
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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.

Subtopic: Â Telescope |
Â 85%
From NCERT
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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

Subtopic: Â Telescope |
Â 82%
From NCERT
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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 cm, 5 cm

2. 190 cm, 10 cm

3. 20 cm, 180 cm

4. 10 cm, 190 cm

Subtopic: Â Telescope |
Â 82%
From NCERT
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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

Subtopic: Â Telescope |
Â 80%
From NCERT
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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

Subtopic: Â Telescope |
Â 67%
From NCERT
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An astronomical telescope has an objective and eyepiece of focal lengths $$40$$ cm and $$4$$ cm respectively. To view an object $$200$$ cm away from the objective, the lenses must be separated by a distance:
1. $$46.0$$ cm
2. $$50.0$$ cm
3. $$54.0$$ cm
4. $$37.3$$ cm

Subtopic: Â Telescope |
Â 64%
From NCERT
NEET - 2016
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The length of an astronomical telescope adjusted for parallel light is 90 cm. If the magnifying power of the telescope is 17, then the focal length of eyepiece and objective are respectively:

 1 10 cm and 80 cm 2 85 cm and 5 cm 3 70 cm and 20 cm 4 5 cm and 85 cm

Subtopic: Â Telescope |
Â 61%
From NCERT
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In an astronomical telescope in normal adjustment a straight black line of length $$L$$ is drawn on inside part of the objective lens. The eye-piece forms a real image of this line. The length of this image is $$l$$. The magnification of the telescope is:
1. $$\frac{L}{l+1}$$
2. $$\frac{L}{l-1}$$
3. $$\frac{L+1}{L-1}$$
4. $$\frac{L}{l}$$

Subtopic: Â Telescope |
Â 61%
From NCERT
NEET - 2015
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