CBSE  /  Class 12  /  Physics  /  Electromagnetic Waves

  • 1. 
    Displacement current is due to:

  • the flow of electrons
  • the Varying electric field
  • the ionization of atmosphere
  • the flow of protons

  • 2. 
    Displacement current is always :

  • equal to conduction current
  • less than conduction current
  • greater than conduction current
  • the sum of current due to flow of positive and negative ions

  • 3. 
    EMW are produced by:

  • charge in uniform motion only
  • charge at rest only
  • accelerated or decelerated charge only
  • all of the above

  • 4. 
    Who first demonstrated the existence of em waves?

  • Hertz
  • Maxwell
  • Ampere
  • Faraday

  • 5. 
    If \(\vec{B}\) is the magnetic field vector and \(\vec{E}\) is the electric field vector in an em wave, then which of the following relations is correct? Here c is the speed of fight:

  • c = \(\frac{E}{B}\)
  • c = BE
  • c = \(\frac{B}{E}\)
  • c = \(\frac{1}{EB}\)

  • 6. 
    The dimensions of E/Bare same as that of:

  • charge
  • current
  • velocity
  • acceleration

  • 7. 
    Name the law which states that a varying electric field produces a magnetic field:

  • Biot-Savart’s law
  • Faraday's law
  • Modified Ampere's law
  • None of these

  • 8. 
    The existence of EMW was experimentally established by :

  • Sir S. C. Bose
  • Maxwell
  • Marconi
  • Hertz

  • 9. 
    An EMW of v = 3 MHz passes from vacuum into dielectric medium with permittivity Er = 4, then:

  • Wavelength is doubled and the frequency remains unchanged
  • Wavelength is doubled and the frequency become half
  • Wavelength is halved and the frequency remains unchanged
  • Wavelength and frequency both remain unchanged

  • 10. 
    Frequency of a wave is 6 × 1015. Hz. The wave is :

  • Radiowave
  • Microwave
  • X-ray
  • Ultra violet
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