181. When an aeroplane attains a speed higher than the speed of sound in air a loud bang is heared. This is because

1. 1. It explodes

   
   
   

   2. Its wings vibrate so violently that the bang is heard

   
   
   

   3. The normal engine noises undergo a Doppler shift to generate the bang

   
   
   

   4. It produces a shock wave which is received as the bang

   
   
   

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   NA

   Correct Option: D

   NA

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182. Consider the following two statements regarding a linearly polarized plane electromagnetic wave
     1. The electric field and the magnetic field have equal average values
     2. The electric energy and magnetic energy have equal average values

1. 1. 1 is false but 2 is true

   
   
   

   2. both 1 and 2 are true

   
   
   

   3. 2 is false but 1 is true

   
   
   

   4. both 1 and 2 are false

   
   
   

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   NA

   Correct Option: B

   NA

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183. As a wave strikes against a wall

1. 1. Its phase changes by 180^°, but velocity does not change

   
   
   

   2. Its phase does not change, but velocity change

   
   
   

   3. Its velocity changes and phase too changes by 180^°

   
   
   

   4. None of the above

   
   
   

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   NA

   Correct Option: A

   NA

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184. Speed of electromagnetic wave is the same

1. 1. For all wavelengths

   
   
   

   2. For all frequencies

   
   
   

   3. In all media

   
   
   

   4. For all intensities

   
   
   

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   NA

   Correct Option: D

   NA

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185. For television broadcasting, the frequency employed is normally

1. 1. 30 - 300 MHx

   
   
   

   2. 30 - 300 GHz

   
   
   

   3. 30 - 300 kHz

   
   
   

   4. 30 - 300 Hz

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: A

   NA

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