131. The echo will be heard if the original sound reflected by an obstacle in

1. 1. 10 s

   
   
   

   2. 0.50 s

   
   
   

   3. 15 s

   
   
   

   4. 0.1 s

   
   
   

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   NA

   Correct Option: D

   NA

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132. The waves used for a communication through artificial satellites are

1. 1. Microwaves

   
   
   

   2. Radio waves in the AM band

   
   
   

   3. Radio waves in the FM band

   
   
   

   4. None of the above

   
   
   

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   NA

   Correct Option: A

   NA

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133. Consider the following statements

1. 1. 1. A flute of smaller length produces waves of lower frequency.
      2. Sound travels in rocks in the of longitudinal elastic waves only.
      Which of the statements given above is / are correct ?

   
   
   

   2. 1 only

   
   
   

   3. 2 only

   
   
   

   4. both 1 and 2

   
   
   

   5. Neither 1 nor 2

   
   
   

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   NA

   Correct Option: B

   NA

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134. Who firstly demonstrated experimentally the existance of electromagnetic wave ?

1. 1. Hertz

   
   
   

   2. Maxwell

   
   
   

   3. Marconi

   
   
   

   4. Newton

   
   
   

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   NA

   Correct Option: A

   NA

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135. When the frequency distribution is normal.

1. 1. Median, mode and mean are all different from one another

   
   
   

   2. Mean, mode and median are identical

   
   
   

   3. Mean is greater than mode

   
   
   

   4. Mean is greater than median

   
   
   

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   NA

   Correct Option: B

   NA

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