Tag: observing space: telescopes

Questions Related to observing space: telescopes

If $\vec{E} = E _0 \cos (kz) \cos (\omega t)\hat{i}$ then $\vec{B}$ for electromagnetic wave is:

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  1. $\vec{B} = \dfrac{E _0}{C} \hat{k}$

  2. $\vec{B} = \dfrac{E _0}{C} \sin (kz) \sin (\omega t)\hat{i}$

  3. $\vec{B} = \dfrac{E _0}{C} \sin (kz) \cos (\omega t) \hat{j}$

  4. $\vec{B} = \dfrac{E _0}{C} \cos (kz) \sin (\omega t) \hat{j}$

Show answer
Correct Option: B
Explanation:

$\dfrac{dE}{dz} = -\dfrac{dB}{dt}$
If $\vec{E} = E _0 \, \cos (kz) \cos (\omega t)$ then
$\vec{B} = \dfrac{E _0}{C} \sin (kz) \sin (\omega t)$ will satisfy the equation

For the propagation of electromagnetic waves

the nature of electromagnetic waves space exploration and forms of light observing space: telescopes electromagnetic waves physics

  1. Medium is required

  2. no medium is required

  3. E and B are in mutually opposite phase

  4. E and b do not contriute

Show answer
Correct Option: B
Explanation:

Electromagnetic waves are a result of changing electric field creating magnetic field and the magnetic field does the same for electric field. Unlike mechanical waves, electromagnetic waves does not require material medium to transfer energy from one place to another.

On the basis of the following features identify correct option:
I. They require no material medium.
II. They are always transverse.
II. They are produced by accelerating charged particles

the nature of electromagnetic waves space exploration and forms of light observing space: telescopes electromagnetic waves physics

  1. Mechanical waves

  2. Electro-magnetic waves

  3. Both (1) and (2)

  4. Neither (1) and (2)

Show answer
Correct Option: B
Explanation:

Electromagnetic waves do not need any material medium for their propagation and they are always transverse in nature e.g. light waves.

A long spring is fixed at one end. A person holding the other end compresses the spring with a jerk. The compression travels along the length of the spring. Which kind of wave is travelled along the length of the spring?

the nature of electromagnetic waves space exploration and forms of light observing space: telescopes electromagnetic waves physics

  1. Electromagnetic waves

  2. Transverse waves

  3. Longitudinal waves

  4. Both (A) and (C)

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Correct Option: C
Explanation:

If the spring is compressed, particles of the spring come close and there is compression.When spring is extended, particles rarefact from each other . Direction of particle motion is in the direction of wave propagation, Hence longitudinal waves  .


In which of the following media can non-mechanical waves travel?

the nature of electromagnetic waves space exploration and forms of light observing space: telescopes electromagnetic waves physics

  1. In vacuum as well as in a medium

  2. In vacuum but not in a medium

  3. In a medium but not in a vacuum

  4. Neither in a medium nor in vacuum

Show answer
Correct Option: A
Explanation:

Non mechanical waves are waves that do not require a medium for transfer of their energy to occur electromagnetic waves are the only type of non mechanical waves.

Non mechanical waves can travel both in vacuum or in any medium

Which of the following have zero average value in a plane electromagnetic wave?
(i) Magnetic field
(ii) Electric field
(iii) Electric energy
(iv) Magnetic energy.

the nature of electromagnetic waves space exploration and forms of light observing space: telescopes electromagnetic waves physics

  1. (i) and (ii)

  2. (i) and (iv)

  3. (ii) and (iii)

  4. (iii) and (iv)

Show answer
Correct Option: A
Explanation:

Electric field has zero average value in electromagnetic waves

What is full form of GMRT ?

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  1. Ground Mobile Receive Terminal

  2. Geometric Mean Reciprocal Titer

  3. Giant Metrewave Radio Telescope

  4. General Maintenance and Repair Technician

Show answer
Correct Option: C
Explanation:

Giant Metrewave Radio Telescope (GMRT).

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:

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

  1. 10 times taller .

  2. 10 times nearer .

  3. 20 times taller .

  4. 20 times nearer .

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Correct Option: D

The waves which can not travel in vacuum are :

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  1. X-rays

  2. radio-waves

  3. infrasonic waves

  4. ultra-viloet rays

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Correct Option: C

Light can pass through

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  1. Vacuum

  2. Glass

  3. Air

  4. All of the above

Show answer
Correct Option: D
Explanation:

Light can pass through vacuum,glass and air.