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प्रश्न
A giant refracting telescope at an observatory has an objective lens of focal length 15 m. If an eyepiece lens of focal length 1.0 cm is used, find the angular magnification of the telescope. If this telescope is used to view the moon, what is the diameter of the image of the moon formed by the objective lens? The diameter of the moon is 3.42 × 106 m and the radius of the lunar orbit is 3.8 × 108 m.
उत्तर
Angular magnification = `- f_0/f_0 (1 +(f_e)/D) = - 1500/1 (1 +1/25) =-1560`
Negative sign indicates that the image is inverted.
Diameter of the image of the moon formed by the objective lens = d (say)
`tan alpha≈alpha = (\text (diameter of moon))/(\text { radius of the orbit}) =d/f_0`
`or ,(3.42 xx 10^6)/(3.8 xx 10^8) = d/15 => d =0.135 m`
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संबंधित प्रश्न
- A giant refracting telescope at an observatory has an objective lens of focal length 15 m. If an eyepiece of focal length 1.0 cm is used, what is the angular magnification of the telescope?
- If this telescope is used to view the moon, what is the diameter of the image of the moon formed by the objective lens? The diameter of the moon is 3.48 × 106 m, and the radius of lunar orbit is 3.8 × 108 m.
- For the telescope is in normal adjustment (i.e., when the final image is at infinity)? what is the separation between the objective lens and the eyepiece?
- If this telescope is used to view a 100 m tall tower 3 km away, what is the height of the image of the tower formed by the objective lens?
- What is the height of the final image of the tower if it is formed at 25 cm?
You are given three lenses of power 0.5 D, 4 D, and 10 D to design a telescope.
1) Which lenses should be used as objective and eyepiece? Justify your answer.
2) Why is the aperture of the objective preferred to be large?
Describe briefly the two main limitations and explain how far these can be minimized in a reflecting telescope ?
Define magnifying power of a telescope. Write its expression.
The eyepiece of an astronomical telescope has a focal length of 10 cm. The telescope is focussed for normal vision of distant objects when the tube length is 1.0. m. Find the focal length of the objective and the magnifying power of the telescope.
Draw a labelled ray diagram showing the formation of an image by a refracting telescope when the final image lies at infinity.
With the help of a ray diagram explain the working of a reflecting telescope.
Draw a ray diagram for the formation of image of an object by an astronomical telescope, in normal adjustment. Obtain the expression for its magnifying power.
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.
