Tag: space exploration and forms of light

Questions Related to space exploration and forms of light

The angular resolution of a radio telescope is to be ${ 0.100 }^{ 0 }$ when the incident beam of wavelength $ 3.00mm$ is used. What is minimum diameter required for the telescope's receiving dish? 

  1. 2.0 m

  2. 4.20 m

  3. 2.20 m

  4. 3.20 m


Correct Option: A

The focal lengths of the objective and eye lens of telescope are respectively $200\ cm$ and $5\ cm$. The maximum magnifying power of the telescope will be.

  1. $-40$

  2. $-48$

  3. $-60$

  4. $-100$


Correct Option: B

An observer looks at a distant tree
of height $10$ m with a
telescope of magnifying power of $20$. To the
observer the tree appears :






.







  1. $10$ times taller.

  2. $10$ times nearer

  3. $20$ times taller.

  4. $20$ times nearer.


Correct Option: D

The angular resolution of a $10cm$ diameter telescope at a  wavelength of $5000A$ is of the order of 

  1. $ 10^{6} \mathrm{rad} $

  2. $ 10^{-2} \mathrm{rad} $

  3. $ 10^{-4} \mathrm{rad} $

  4. $ 10^{-6} \mathrm{rad} $


Correct Option: D

In a terrestrial telescope, the telescope, the focal length of objective is 90 cm of inverting lens is 5 cm and of eye lens is 6 cm. If the final image is at 3  cm, then the magnification will be

  1. 21

  2. 12

  3. 15

  4. 18


Correct Option: C

The focal lengths of the objective and eye plece of astronomical telescope are $100cm$ and $2cm$ respectively. The magnitude of magnifying power of telescope for adjustment is

  1. $54$

  2. $0.02$

  3. $50$

  4. $100$


Correct Option: A

The focal length of an objective of a telescope is 3 meter and diameter 15 cm. Assuming for a normal eye, the diameter of the pupil is 3 mm for its complete use, the focal length of eye piece must  be

  1. $6 cm$

  2. $6.3 cm$

  3. $20 cm$

  4. $60 cm$


Correct Option: A

The diameter of the lens of a telescope is $1.22m$. The wavelength of light of $5000\mathring {A}$. The resolving power of the telescope is _____

  1. $5\times{10}^{-5}$

  2. $5\times{10}^{-6}$

  3. $5\times{10}^{-7}$

  4. $5\times{10}^{-4}$


Correct Option: C

An astronomical telescope and a Galilean telescope use identical objective lenses. They have the same magnification, when both are in normal adjustment. The eyepiece of the astronomical telescope has a focal length f.

  1. The tube length of the two telescope differ by f.

  2. The tube length of the two telescopes differ by 2f.

  3. The Galileans telescope has shorter tube length.

  4. The Galileans telescope has longer tube length.


Correct Option: B,C
Explanation:

In normal adjustment, tube length of an astronomical telescope is $ \left( { f } _{ 0 }+{ f } _{ e } \right) $ and that of Galilean telescope is $ \left( { f } _{ 0 }+{ f } _{ e } \right) $, where $ { f } _{ 0 }$ and $ { f } _{ e }$ are the focal lengths of the objective and the eyepiece respectively. 


$ Here,\quad { f } _{ e }=f$

magnification  =$ \dfrac { { f } _{ 0 } }{ { f } _{ e } } $ for both telescope.

A terrestrial telescope is made by introducing an erecting lens of focal length, $f$, between the objective and eyepiece lens of an astronomical telescope. This causes the length of telescope tube to increase by an amount equal to

  1. $f$

  2. $2f$

  3. $3f$

  4. $4f$


Correct Option: D
Explanation:

Since, the mInimum distance between the real object and real image is $4f$. 

Therefore length of telescope increase by $4f$.