Tag: introduction to electromagnetic waves

Questions Related to introduction to electromagnetic waves

According to Maxwell's hypothesis, changing of electric filed give rise to

physics option a: relativity maxwell's equations the nature of light introduction to electromagnetic waves

  1. magnetic field

  2. pressure gradient

  3. charge

  4. voltage

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Correct Option: A
Explanation:

According to Maxwell's hypothesis, changing of electric field gives rise to Magnetic field.

We know that $F=qE,$, where $F$ is force and $E$ is electric field.
We can relate magnetic field and force by $F=qvB$, where $v$ is velocity and $B$ is the magnetic field.
Therefore we can obtain magnetic field by changing electric field.
Therefore option $A$ is correct.

Unpolarized light falls first on polarizer $\left( P \right) $ and then on analyzer $\left( A \right) $. If the intensity of the transmitted light from the analyser is $\dfrac { 1 }{ 8 }$th of the incident unpolarized light. What will be the angle between optic axes of $P$ and $A$?

physics option a: relativity maxwell's equations the nature of light introduction to electromagnetic waves

  1. ${ 45 }^{ o }$

  2. ${ 30 }^{ o }$

  3. Zero

  4. ${ 60 }^{ o }$

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Correct Option: D
Explanation:

Given,
$I=\dfrac { { I } _{ 0 } }{ 2 } $              ....(i)
${ I }^{ ' }=I\cos ^{ 2 }{ \theta  } $                 $\left( \because { I }^{ ' }=\dfrac { { I } _{ 0 } }{ 8 }  \right) $
$\therefore \dfrac { { I } _{ 0 } }{ 8 } =\dfrac { { I } _{ 0 } }{ 2 } \cos ^{ 2 }{ \theta  } $
From the equation (i), we have
$\dfrac { 1 }{ 4 } =\cos ^{ 2 }{ \theta  } \Rightarrow \cos { \theta  } ={ 1 }/{ 2 }$
$\Rightarrow \cos { \theta  } =\cos { { 60 }^{ o } } $
$\Rightarrow \theta ={ 60 }^{ o }$

A plane electromagnetic wave with an intensity of $200 W/m^2$ is incident normal to a flat plate of radius 30 cm. If the plate absorbs $60%$ and reflect $40%$ of the incident radiation, what is the momentum transferred to it in 5 min?

physics option a: relativity maxwell's equations the nature of light introduction to electromagnetic waves

  1. $1.7 \times 10^{-3} kg ms^{-1}$

  2. $2.7 \times 10^{-4} kg ms^{-1}$

  3. $3.7 \times 10^{-4} kg ms^{-1}$

  4. $3.7 \times 10^{-3} kg ms^{-1}$

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Correct Option: A

Fill the blank space with the best suitable option. All electromagnetic waves have the same _________ while travelling in a vacuum.

physics electromagnetic waves and communication system maxwell's equations the nature of light introduction to electromagnetic waves

  1. amplitude

  2. frequency

  3. wavelength

  4. Intensity

  5. speed

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Correct Option: E
Explanation:

All electromagnetic waves (EM waves) travel with the speed of light in vacuum but these have different frequency, amplitude, wavelength and intensity.

Thus option E is correct.

This question has statement-1 and statement-2. Of the four choices given after the Statements, choose the one that best describes the two statements.
Statement 1: Short wave transmission is achieved due to the total internal reflection of the e-m wave from an appropriate height in the ionosphere.
Statement 2: Refractive index of a plasma is independent of the frequency of e-m waves.

physics electromagnetic waves and communication system maxwell's equations the nature of light introduction to electromagnetic waves

  1. Statement 1 is true, Statement 2 false.

  2. Statement 1 is false, Statement 2 is true

  3. Statement 1 is true, Statement 2 is true but statement 2 is not the correct of statement 1.

  4. Statement 1 is true, statement 2 is true and statement 2 is the correct explanation of statement 1.

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Correct Option: C

The waves which can not travel in vacuum are :

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

  1. X-rays

  2. radio-waves

  3. infrasonic waves

  4. ultra-viloet rays

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Correct Option: C

Light can pass through

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

  1. Vacuum

  2. Glass

  3. Air

  4. All of the above

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Correct Option: D
Explanation:

Light can pass through vacuum,glass and air.

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