12th Class Physics EM Waves Question Bank

done MCQs - Electromagnetic Waves Total Questions - 16

• question_answer1)
  A linearly polarized electromagnetic wave given as \[E\,\,=\,\,{{E}_{0}}\]\[i\,\,cos\,\,(kz-\omega t)\] is incident normally on a perfectly reflecting infinite wall at \[z=a\]. Assuming that the material of the wall is optically inactive, the reflected wave will be given as
  A)
  \[{{\operatorname{E}}_{r}}=-{{E}_{0}}\hat{i}\,cos\ \,(kz-\omega t)\] done clear
  B)
  \[{{\operatorname{E}}_{r}}={{E}_{0}}\hat{i}\ \,cos\ \,(kz+\omega t)\] done clear
  C)
  \[{{E}_{r}}=-{{E}_{0}}\hat{i}\ \,cos\ \,(kz+\omega t)\] done clear
  D)
  \[{{\operatorname{E}}_{r}}={{E}_{0}}\hat{i}\ \,\sin \ \,(kz+\omega t)\] done clear
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• question_answer2)
  Light with an energy flux of \[20W/c{{m}^{2}}\] falls on a non-reflecting surface at normal incidence. If the surface has an area of \[30c{{m}^{2}}\], the total momentum delivered (for complete absorption) during 30 minutes is
  A)
  \[36 \times  1{{0}^{-5}} kg m/s.\]    done clear
  B)
  \[36 \times  1{{0}^{-4}} kg m/s.\] done clear
  C)
  \[108 \times  1{{0}^{4}} kg m/s.\]   done clear
  D)
  \[1.08 \times  1{{0}^{7}} kg m/s.\] done clear
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• question_answer3)
  The electric field intensity produced by the radiations coming from \[100\text{ }W\] bulb at a \[3\text{ }m\] distance is E. The electric field intensity produced by the radiations coming from 50 W bulb at the same distance is
  A)
  \[\frac{\operatorname{E}}{2}\] done clear
  B)
  2E done clear
  C)
  \[\frac{\operatorname{E}}{\sqrt{2}}\] done clear
  D)
  \[\sqrt{2}\]E done clear
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• question_answer4)
  If \[\vec{E}\] and \[\vec{B}\] represent electric and magnetic field vectors of the electromagnetic wave, the direction of propagation of electromagnetic wave is along
  A)
  \[\overset{\to }{\mathop{{}}}\,\] done clear
  B)
  \[\vec{B}\] done clear
  C)
  \[\vec{B}\,\times \,\vec{E}\] done clear
  D)
  \[\vec{E}\,\times \,\vec{B}\] done clear
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• question_answer5)
  The ratio of contributions made by the electric field and magnetic field components to the intensity of an EM wave is
  A)
  \[c:1\] done clear
  B)
  \[{{c}^{2}}:1\] done clear
  C)
  \[1:1\] done clear
  D)
  \[\sqrt{c}:1\] done clear
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• question_answer6)
  An EM wave radiates outwards from a dipole antenna, with \[{{E}_{0}}\] as the amplitude of its electric field vector. The electric field \[{{E}_{0}}\] which transports significant energy from the source falls off as
  A)
  \[\frac{1}{{{r}^{3}}}\] done clear
  B)
  \[\frac{1}{{{r}^{2}}}\] done clear
  C)
  \[\frac{1}{r}\] done clear
  D)
  remains constant done clear
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• question_answer7)
  In electromagnetic waves, the phase difference between magnetic and electric field vectors is       
  A)
  zero done clear
  B)
  \[\pi \]                       done clear
  C)
  \[\pi /2\] done clear
  D)
  \[\pi /4\] done clear
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• question_answer8)
  From Maxwell's hypothesis, a changing electric field gives rise to
  A)
  An electric field done clear
  B)
  An induced emf  done clear
  C)
  A magnetic field done clear
  D)
  A magnetic torque. done clear
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• question_answer9)
  One requires \[11\text{ }eV\] of energy to dissociate a carbon monoxide molecule into carbon and oxygen atoms. The minimum frequency of the appropriate electromagnetic radiation to achieve the dissociation lies in
  A)
  Visible region done clear
  B)
  Infrared region done clear
  C)
  Ultraviolet region done clear
  D)
  Microwave region done clear
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• question_answer10)
  The phenomenon which shows quantum nature of electromagnetic radiation is
  A)
  Piezoelectric effect done clear
  B)
  Photoelectric effect done clear
  C)
  Hall effect done clear
  D)
  Tyndall effect done clear
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• question_answer11)
  The electromagnetic radiations used for water purification and eye surgery is
  A)
  Infrared done clear
  B)
  Microwave done clear
  C)
  X-rays done clear
  D)
  None of the above done clear
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• question_answer12)
  Electromagnetic wave having frequency
  A)
  Ultraviolet wave done clear
  B)
  Radio wave done clear
  C)
  Microwave done clear
  D)
  X-rays done clear
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• question_answer13)
  Proper arrangement of Gamma rays. Microwave, IR wave and UV rays in ascending order of frequency is
  A)
  Gamma rays > UV rays > IR rays > Microwave done clear
  B)
  Microwave > IR rays > UV rays > Gamma rays done clear
  C)
  UV rays > Gamma rays > Microwave > IR   rays done clear
  D)
  IR rays > UV rays > Microwave > Gamma rays done clear
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• question_answer14)
  In vacuum, the physical property which remains same for microwave of wavelength \[1\text{ }mm\] and UV radiation \[1600\overset{o}{\mathop{A}}\,\] is
  A)
  Wavelength done clear
  B)
  Frequency done clear
  C)
  Speed done clear
  D)
  None of the above done clear
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• question_answer15)
  In vacuum, the wavelength of the electromagnetic wave of frequency \[5\,\times \,{{10}^{19}}\text{ }Hz\] is
  A)
  \[6\times {{10}^{-12}}\operatorname{m}\] done clear
  B)
  \[3\times {{10}^{-8}}\operatorname{m}\] done clear
  C)
  \[1.6\times {{10}^{11}}\operatorname{m}\] done clear
  D)
  \[15\times {{10}^{27}}\operatorname{m}\] done clear
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• question_answer16)
  Which one of the following statements are correct?
  A)
  X-rays are suitable for radar system and aircraft navigation. done clear
  B)
  Water molecules readily absorb infrared radiation and their thermal motion increases. done clear
  C)
  Microwaves are produced in Coolidge tube done clear
  D)
  Gamma radiations generate due to electron transitions between upper and lower energy levels of heavy element when excited by electron bombardment done clear
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