Tag: optical telescope

Questions Related to optical telescope

The focal length of the objective of an astronomical telescope is 1 m and it is in normal adjustment.Initially the telescope is focussed to a heavenly body. If the same telescope is to be focussed to an object at a distance of 21 m from the objective,then identify the correct choice

physics option c: imaging optical instruments : telescope the reflecting telescope optical telescope xx radio telescope and space telescopes

  1. eye piece should be displaced by 2 cm away from the objective

  2. eye piece should be displaced by 2 cm towards the objective

  3. eye piece should be displaced by 5 cm towards the objective

  4. eye piece should be displaced by 5 cm away from the objective

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Correct Option: D
Explanation:

We know, $ \dfrac {1}{f} = \dfrac {1}{v} - \dfrac {1} {u} $


We seeing heavenly body,  $u =  \infty$
$v = f = 1 m$

When seeing 21 m far
$u = - 21 m $
$f = 1 m$
$v = \dfrac {f u} {(f+u)} = 21 / 20 = 1.05 m$

So, eye piece need to move $1.05-1 = 0.05 m$ further away from objective

Answer. D) eye piece should be displaced by $5 cm$ away from the objective

The focal lengths of the objective and eyepiece of a telescope are 60cm and 5cm respectively.The telescope is focused on an object 360cm from the objective and the final image is formed at a distance of 30cm from the eye of the observer. The length of the telescope is

physics option c: imaging optical instruments : telescope the reflecting telescope optical telescope xx radio telescope and space telescopes

  1. 66.3 cm

  2. 86.3 cm

  3. 76.3 cm

  4. 96.3 cm

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Correct Option: C
Explanation:

$f _o = 60cm$


$f _e = 5cm$

$r _e = 30cm$

$L = ?$

$u _o = 360cm$

$\dfrac {1}{v _o} + \dfrac {1}{360} = \dfrac {-1}{60}$

$\dfrac {1}{v _o} = \dfrac {-1}{60} + \dfrac {1}{360}$

In which of the following instruments is the final image virtual?

physics observing space: telescopes optical instruments : telescope the reflecting telescope optical telescope xx radio telescope and space telescopes

  1. Projector

  2. Camera

  3. Microscope

  4. Telescope

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Correct Option: C,D
Explanation:

The final image of the camera and projector is real because it is obtained or projected on a screen or a photographic film or a chip.

A simple microscope uses convex lens and the object is placed between the focus and the optical center, so that, an erect, virtual and enlarged image of the object is formed.

A telescope uses two co-axially placed convex lenses in such a way that the focus of objective lens is past the focus of the eye piece. The first lens or the objective lens produces a real and inverted image of the object to be observed and this real image formed acts as an object for the eye piece convex lens and is between the focus and the optical center, so that, an inverted, virtual and enlarged image of the object is formed.

Hence, the correct answers are OPTIONS C and D.  

A planet is observed by an astronomical reflecting telescope having an objective of focal length $16 m$ and an eye-piece of focal length $2 cm$. Then :

physics option c: imaging optical instruments : telescope the reflecting telescope optical telescope xx radio telescope and space telescopes

  1. the distance between the objective and the eye - piece is $16.02 m$

  2. the angular magnification of the planet is $800$

  3. the image of planet is erect

  4. the objective is larger than eye - piece

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Correct Option: A,B,D
Explanation:

A telescope uses two co-axially placed convex lenses in such a way that the focus of objective lens is past the focus of the eye piece as evident here from the focal lengths of the objective lens and the eye piece. $ \therefore $ The objective lens is larger than eye piece.

Length of the tube is given as 
$ L = f _o + f _e = 16\ m + 2\ cm = 16.02\ m $

Angular magnification is given as:
$ m = \dfrac{f _o}{f _e} = \dfrac{1600}{2} = 800 $


Since, the first lens or the objective lens produces a real and inverted image of the object to be observed and this real image formed acts as an object for the eye piece convex lens and is between the focus and the optical center, so, an inverted, virtual and enlarged image of the object is formed. $ \therefore $ The final image is inverted. 

Hence, the correct answers are OPTIONS A,B and D.

An astronomical refracting telescope will have large angular magnification and high angular resolution, when it has an objective lens of

physics option c: imaging optical instruments : telescope the reflecting telescope optical telescope xx radio telescope and space telescopes

  1. large focal length and small diameter

  2. large focal length and large diameter

  3. small focal length and large diameter

  4. small focal length and small diameter

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Correct Option: B

Salyut 6 and Salyut 7, were built with:

geography space travel space research and satellites space exploration and forms of light optical telescope

  1. three docking ports

  2. two docking ports

  3. five docking ports

  4. No docking ports

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Correct Option: B
Explanation:

Salyut 6 and Salyut 7 were the second generation of the Salyut programme which was the first space station programme undertaken by the Soviet Union. They both were built with two docking ports, one on either end of the station.

The space stations so far launched are broadly classified into two types:

geography space travel space research and satellites space exploration and forms of light optical telescope

  1. Mir and Skylab

  2. Apollo and Salyut

  3. Monolithic and Modular

  4. Almaz and Salyut

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Correct Option: C
Explanation:

The space station launched are broadly classified into two types: 

  1. Monolithic : earlier space station, Salyut and Skylab in which were constructed and launched in one piece, and then manned by a crew later. 
  2. Modular: Mir and ISS, a core unit was launched, and additional modules, generally with a specific role, were later added to that.

Salyut and Skylab were built:

geography space travel space research and satellites space exploration and forms of light optical telescope

  1. monolithic

  2. duo lithic

  3. trilithic

  4. None of these

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Correct Option: A
Explanation:

Salyut and Skylab were built monolithic meaning that they were constructed and launched in one piece, and then manned by a crew later. 

Which of the following is cannot be considered as the use of space stations?

geography space travel space research and satellites space exploration and forms of light optical telescope

  1. Space station is used to study the effects of long-duration spaceflight on the human body

  2. Space station provides a platform for greater number and length of scientific studies than it is available on other space vehicles.

  3. Space stations are used both for military and civilian purposes.

  4. None of these

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Correct Option: D
Explanation:

Space stations are made to conduct experiments that needs to be done out in space. It is used to study the effects of long-duration space flight on human body. These provides a platform for greater number and length of scientific studies than it is available on other space vehicles and other military and civilian purposes.