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प्रश्न
State the condition under which a large magnification can be achieved in an astronomical telescope.
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उत्तर १
Condition under which a large magnification can be achieved in an astronomical telescope:
In astronomical telescope, the light is incident from infinity on the objective lens and it forms image at the focus of the objective lens and for large magnification the length between the lens is so adjusted that the final image is formed at the least distance of the distinct vision from the eyepiece
Magnification of astronomical telescope is
\[(M . P )_\max = - \frac{f_o}{f_e}(1 + \frac{f_e}{d})\] To have large magnification power, \[f_o\] must be large as possible and \[f_e\] must be as small as possible.
उत्तर २
By increasing the focal length of objective lens and at the same time keeping the focal length of eye peice minimum we can increase the magnifying power of telescope
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)?
Draw a ray diagram depicting the formation of the image by an astronomical telescope in normal adjustment.
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
Describe briefly the two main limitations and explain how far these can be minimized in a reflecting telescope ?
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.
Define the term ‘resolving power of a telescope’.
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.
In an astronomical telescope in normal adjustment, a straight black line of length L is drawn on the objective lens. The eyepiece forms a real image of this line whose length is 𝑙. What is the angular magnification of the telescope?
