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Electromagnetic Waves — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsElectromagnetic Waves4 Marks
Question
In an electromagnetic wave both the electric and magnetic fields are perpendicular to the direction of propagation, that is why electromagnetic waves are transverse in nature. Electromagnetic waves carry energy as they travel through space and this energy is shared equally by the electric and magnetic fields. Energy density of an electromagnetic waves is the energy in unit volume of the space through which the wave travels.
  1. The electromagnetic waves propagated perpendicular to both $\vec{\text{E}}$ and $\vec{\text{B}}.$ The electromagnetic waves travel in the direction of.
  1. $\vec{\text{E}}\times\vec{\text{B}}$
  2. $\vec{\text{E}}\times\vec{\text{B}}$
  3. $\vec{\text{B}}\times\vec{\text{E}}$
  4. $\vec{\text{B}}\times\vec{\text{E}}$
  1. Fundamental particle in an electromagnetic wave is:
  1. Photon
  2. Electron
  3. Phonon
  4. Proton
  1. Electromagnetic waves are transverse in nature is evident by:
  1. Polarisation
  2. Interference
  3. Reflection
  4. Diffraction
  1. For a wave propagating in a medium, identify the property that is independent of the others.
  1. Velocity
  2. Wavelength
  3. Frequency
  4. All these depend on each other.
  1. The electric and magnetic fields of an electromagnetic waves are:
  1. In opposite phase and perpendicular to each other.
  2. In opposite phase and parallel to each other.
  3. In phase and perpendicular to each other.
  4. In phase and parallel to each other.
✓

Answer

  1. (b) $\vec{\text{E}}\times\vec{\text{B}}$
Explanation:

Electromagnetic waves propagate in the direction of $\vec{\text{E}}\times\vec{\text{B}}.$
  1. (a) Photon
Explanation:

Photon is the fundamental particle in an electromagnetic wave.
  1. (a) Polarisation
Explanation:

Polarisation establishes the wave nature of electromagnetic waves.
  1. (c) Frequency
Explanation:

Frequency u remains unchanged when a wave propagates from one medium to another. Both wavelength and velocity get changed.
  1. (c) In phase and perpendicular to each other.
Explanation:

The electric and magnetic fields of an electromagnetic wave are in phase and perpendicular to each other.

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