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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)?
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उत्तर
Focal length of the objective lens, fo = 140 cm
Focal length of the eyepiece, fe = 5 cm
Least distance of distinct vision, d = 25 cm
(a) When the telescope is in normal adjustment, its magnifying power is given as:
`"m" = "f"_"o"/"f"_"e"`
= `140/5`
= 28
(b) When the final image is formed at d, the magnifying power of the telescope is given as:
`"f"_"o"/"f"_"e" [1 + "f"_"e"/"d"]`
= `140/5 [1 + 5/25]`
= 28[1 + 0.2]
= 28 × 1.2
= 33.6
संबंधित प्रश्न
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Write the two important factors considered to increase the magnifying power?
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Write two important limitations of a refracting telescope over a reflecting-type telescope.
The focal lengths of the objective and eyepiece of a microscope are 1.25 cm and 5 cm respectively. Find the position of the object relative to the objective in order to obtain an angular magnification of 30 in normal adjustment.
A Galilean telescope is 27 cm long when focussed to form an image at infinity. If the objective has a focal length of 30 cm, what is the focal length of the eyepiece?
(i) What is meant by resolving power of a telescope?
(ii) State any one method of increasing the resolving power of an astronomical 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?
An optical instrument that uses objective and eyepiece lenses to magnify distant terrestrial or celestial objects is called a:
A telescope in which the eye lens used is concave, so that the final image is erect, is popularly called a:
In the working idea of a telescope's magnifying power, the beam of incident rays is inclined at an angle \[\alpha\] with the principal axis, while the emergent beam is inclined at a greater angle \[\beta\]. This produces:
During the formation of an image in a telescope under normal adjustment, the eyepiece is adjusted so that the intermediate image lies:
The resolving power of a telescope is defined as:
According to Rayleigh's criterion for the angular separation between two resolvable objects, the correct relation is:
