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Blow a balloon and let it go. You will find it moving in the direction opposite to the direction in which the air is ejected. This demonstrates :

physics satellite launch vehicles rocket propellants universe and space science xx radio telescope and space telescopes launching vehicles

  1. the principle of rocket propulsion

  2. the principle of combustion

  3. the principle of conservation of energy

  4. None of the above

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Correct Option: A
Explanation:

The principle of rocket propulsion works on the 'Newton's Third Law of Motion'. It states that, 'to every action, there is always an equal and opposite reaction'.

In the case of a rocket, the engine emits hot burning gases in the downward direction. These gases apply an equal and opposite reaction force to the rocket in the upward direction.
This is how a rocket is propelled.
Rocket propulsion is similar to the example of the situation in which, if we blow a balloon and let it go, it starts moving in the direction opposite to the direction in which the air is ejected. 
Balloon forces out the air inside it. The air applies an equal and opposite reaction force to the balloon.

The scientific instrument which is usually placed in the front region of the rocket is called :

physics satellite launch vehicles rocket propellants universe and space science xx radio telescope and space telescopes launching vehicles

  1. PAYBOOK

  2. PLAYOAD

  3. PAYLOAD

  4. PLAYWOOD

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Correct Option: C
Explanation:

The scientific instrument placed in the front region of the rocket is called PAYLOAD. For a rocket payload can be a satellite, space probe or a space craft carrying humans. The fraction of payload to the total liftoff weight of the rocket iscalled as palyload friction.

The principle of rocket propulsion depends on :

physics satellite launch vehicles rocket propellants universe and space science xx radio telescope and space telescopes launching vehicles

  1. Newton's third law of motion

  2. Principle of conservation of momentum

  3. Either A and B

  4. Both A and B

Show answer
Correct Option: D
Explanation:

The principle of rocket propulsion works on the 'Newton's Third Law of Motion'. It states that, 'to every action, there is always an equal and opposite reaction'.

In the case of a rocket, the engine emits hot burning gases in the downward direction. These gases apply an equal and opposite reaction force to the rocket in the upward direction.
This is how a rocket is propelled.
The principle of conservation of momentum states that whenever two bodies collide or get separated, then their  total momentum before collision or separation is equal to their total momentum after collision or separation.
Since the gases of the rocket and the rocket are stationery at the start, their total momentum is zero. After the gases start burning, the momentum imparted to the rocket is equal and opposite to that of the gases. Hence their total momentum is zero.

A reflecting telescope has a large mirror for its objective with radius of curvature equal to 80 cm. The magnifying power of this telescope if eye piece used has a focal length of 1.6 cm is:

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

  1. 100

  2. 50

  3. 25

  4. 5

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Correct Option: C
Explanation:

The focal length of objective mirror $f _0 = \dfrac{R}{2} = \dfrac{80}{2} = 40 \,cm$
and focal length of eye piece = 1.6 cm
$\therefore $ magnifying power, $m = \dfrac{f _0}{f _e} = \dfrac{40}{1.6 } = 25$

A telescope is used to resolve two stars separated by $4.6 \, \times \, 10^{-6}$ rad. If the wavelength of light used is 5460 $\overset{0}{A}$, what should be the aperture of the objective of the telescope? 

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

  1. 0.1488 m

  2. 0.567 m

  3. 1 m

  4. 2 m

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Correct Option: A
Explanation:

Aperature of the telescope, $D = \dfrac{1.22\lambda}{d\theta}$ 


Here, $\lambda = 5460\ \overset{0}{A} = 5460 \times 10^{-10}m$


$ d\theta= 4.6 \times10^{-6}\ rad$

$\therefore D = \dfrac{1.22\times5460\times10^{-10}}{4.6\times 10^{-6}}$
$ = 0.1488m $

If you want to make Refracting Telescope, what components will you choose ?

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

  1. One convex led and one concave lens.

  2. Two convex lenses.

  3. One concave mirror, one plane mirror and one convex lens.

  4. Once concave mirror, one convex mirror and one convex lens.

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Correct Option: B
Which material should be chosen to make the concave mirrors of a high resolution telescope so that it can also withstand temperature variations?
physics option c: imaging optical instruments : telescope the reflecting telescope optical telescope xx radio telescope and space telescopes

  1. Quartz

  2. Flint glass

  3. Crown glass

  4. Combination of Flint and Silica

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Correct Option: A
Explanation:

Quartz makes an ideal mirror. Its high hardness results in the smoothest micropolished surface possible, and its thermal dimensional stability allows the optician to produce a flat surface with almost no edge defects.

Scientists identify the elements that are burning in the stars by using which of the following devices?

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

  1. Refractive telescopes

  2. Reflective telescopes

  3. Spectroscopes

  4. Polarimeters

  5. Photoelectric mircoscopes

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Correct Option: C
Explanation:
Using the spectroscope, scientists can separate the individual line spectra of the elements that are burning in the stars and therefore identify the elements.

Two convex lenses of focal length 0.3 m and 0.05 m are used to make a telescope. The distance kept between them is equal to 

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

  1. 0.35 m

  2. 0.25 m

  3. 0.175 m

  4. 0.15 m

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Correct Option: A
Explanation:

To make a Telescope,
$L= f _{0}+f _{e}$

$= 0.3+0.05$

$= 0.35m$

In an astronomical telescope of refracting type:

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

  1. Eyepiece has greater focal length

  2. Objective has greater focal length

  3. Objective and eyepiece have equal focal length

  4. Eyepiece has greater aperture than the objective

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Correct Option: B
Explanation:

An astronomical telescope of refracting type has objective of greater focal length to have more surface area for incoming light from celestial bodies.