Tag: observing space: telescopes

Questions Related to observing space: telescopes

Identify the electromagnetic wave which is most often used in medicine for diagnostic imaging?

physics observing space: telescopes maxwell's equations the nature of light introduction to electromagnetic waves

  1. infrared

  2. ultraviolet

  3. microwave

  4. radio

  5. gamma ray

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Correct Option: A
Explanation:

During diagnosis of the body heat signatures of the organs are vital. These heat waves lie in the infrared region of the spectrum.

Therefore, infrared waves are used in diagnostic imaging.

 Option A is, therefore, correct. 

Which of the following is responsible for passing the energy from one to the another to transmit the light waves.

physics observing space: telescopes maxwell's equations the nature of light introduction to electromagnetic waves

  1. atom

  2. neutron

  3. fiber

  4. object

  5. wavelength

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Correct Option: A
Explanation:

Answer A is correct 

Atom is responsible for transmission of light.
By collision of atoms they passes energy from one to another and hence light is transmitted. 

Identify the medium required for Electromagnetic waves to travel?

physics observing space: telescopes maxwell's equations the nature of light introduction to electromagnetic waves

  1. none

  2. liquid

  3. solid

  4. gas

  5. fluid (liquid or gas)

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Correct Option: A
Explanation:

Electromagnetic wave does not require any material medium to propagate. These can also travel through vacuum. Also EM waves travel with the speed equal to that of light  i.e $3 \times 10^8$ m/s

Identify which of the following best describe the difference between electromagnetic (EM) waves and other types of waves?

physics observing space: telescopes maxwell's equations the nature of light introduction to electromagnetic waves

  1. EM waves can travel without a medium.

  2. EM waves are higher in frequency than all other waves

  3. EM waves have shorter wave lengths than any other type of wave.

  4. EM waves transport matter and energy.

  5. EM waves require a medium to travel.

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Correct Option: A
Explanation:

EM waves do not require a material medium to travel, these can propagate even through vacuum while all other waves require a certain medium to travel.

Which of the following is an electromagnetic waves that cause sunburn?

physics observing space: telescopes maxwell's equations the nature of light introduction to electromagnetic waves

  1. ultraviolet

  2. X-rays

  3. infrared

  4. microwaves

  5. gamma rays

Show answer
Correct Option: A
Explanation:

UV waves are shorter than visible light waves, so UV possesses more energy than regular light.

UV photons have the right energies to cause chemical changes. When UV light hits your skin, the DNA in your skin cells can undergo chemical change. This chemical change is what sunburn is. In extreme cases, this change in DNA can result in cancer.

In an electormagnetic wave, the phase difference between electric field $\vec { E }$ and magnetic field $ \vec { B } $ is :

physics observing space: telescopes maxwell's equations the nature of light introduction to electromagnetic waves

  1. $\dfrac { \pi }{ 4 } $

  2. $\dfrac { \pi }{ 2 } $

  3. $\pi $

  4. Zero

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Correct Option: D
Explanation:

The electric and magnetic field components of a linearly polarized electromagnetic wave oscillate in such a way that they peak at the same time and they become zero at the same time but they point to different directions in space, separated by an angle of $90^{\circ}$.


Since there is no time difference between the peaks of the electric and magnetic oscillations the phase difference between the electric and magnetic field vectors of a linearly polarized electromagnetic wave is zero.

Electromagnetic wave is deflected by

physics observing space: telescopes maxwell's equations the nature of light introduction to electromagnetic waves

  1. Electric field

  2. Magnetic field

  3. Both ( 1 ) & ( 2 )

  4. Neither electric field nor magnetic field

Show answer
Correct Option: D
Explanation:

EM waves are formed by electric and magnetic fields but are not deflected by them, and also they can be deflected by gravitational field....

 Light (electromagnetic wave) has an electric and a magnetic field and should thus deflect a compass needle during daytime.

Visible light - Being an Electromagnetic wave is reflected by glass (take mirror).

For highly intense X-Rays & gamma rays, take that the mirror is stronger such that it could resist for at least 30 seconds.

hence, light wave neither electric field nor magnetic field

Wavelength of an electron having energy 10KeV is ...........$ A^0 $

physics observing space: telescopes maxwell's equations the nature of light introduction to electromagnetic waves

  1. 0.12

  2. 1.2

  3. 12

  4. 120

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Correct Option: C

An electromagnetic wave in vacuum has the electric and magnetic field $\overset { \rightarrow  }{ E } $ and $\overset { \rightarrow  }{ B } $  which are always perpendicular to each other. If the direction of polarization is given by $\overset { \rightarrow  }{ X }  $ and that of wave propagation by $\overset { \rightarrow  }{ k } $ then:

physics observing space: telescopes maxwell's equations the nature of light introduction to electromagnetic waves

  1. $\overset { \rightarrow }{ X } \parallel \overset { \rightarrow }{ B } $ and $\overset { \rightarrow }{ k } \parallel \overset { \rightarrow }{ B\times } \overset { \rightarrow }{ E } $

  2. $\overset { \rightarrow }{ X } \parallel \overset { \rightarrow }{ E } $ and $\overset { \rightarrow }{ k } \parallel \overset { \rightarrow }{ E\times } \overset { \rightarrow }{ B } $

  3. `$\overset { \rightarrow }{ X } \parallel \overset { \rightarrow }{ B } $ and $\overset { \rightarrow }{ k } \parallel \overset { \rightarrow }{ E\times } \overset { \rightarrow }{ B } $

  4. $\overset { \rightarrow }{ X } \parallel \overset { \rightarrow }{ E } $ and $\overset { \rightarrow }{ k } \parallel \overset { \rightarrow }{ B\times } \overset { \rightarrow }{ E } $

Show answer
Correct Option: C
Explanation:

In an electromagnetic wave, electrical and magnetic fields are perpendicular to each other. The wave propagates in a direction perpendicular to both electric and magnetic fields as given by  $\vec E\times \vec B$.

So, the direction of propagation of the wave will be perpendicular to the to the direction of oscillation of the fields.
$\overset { \rightarrow }{ k } \parallel \overset { \rightarrow }{ B\times } \overset { \rightarrow }{ E } $
And the direction of polarization must be perpendicular to the electric field and parallel to the magnetic field.
$\vec X||\vec E$.
The correct option is $(B)$.

Electro-magnetic wave can be:

physics observing space: telescopes maxwell's equations the nature of light introduction to electromagnetic waves

  1. Transverse in nature

  2. longitudinal in nature

  3. Both

  4. Electrical in nature

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Correct Option: C