176. The ionosphere is mainly composed of

1. 1. Nitrogen and oxygen

   
   
   

   2. Ozone

   
   
   

   3. Electrons and positive ions

   
   
   

   4. None of the above

   
   
   

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   NA

   Correct Option: C

   NA

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177. The ozone layer absorbs radiation of wavelengths

1. 1. Less than 3 x 10^-5 m

   
   
   

   2. More than 3 x 10^-7 m

   
   
   

   3. Less than 3 x 10^-5 m

   
   
   

   4. Less than 3 x 10^-5 m

   
   
   

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   NA

   Correct Option: A

   NA

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178. Consider the following statements :
     Assertion (A) : The velocity of sound in air increases due to the presence of moisture in it
     Reason (R) : The presence of moisture in air lowers the density of air of these statements
     Codes

1. 1. Both A and R are true and R is the correct explanation of A

   
   
   

   2. Both A and R are true but R is not the correct explanation of A

   
   
   

   3. A is true but R is false

   
   
   

   4. A is false but R is true

   
   
   

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   NA

   Correct Option: A

   NA

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179. The temperature at which the speed of sound in air becomes double of its value at 27°C is

1. 1. 54°C

   
   
   

   2. 327°C

   
   
   

   3. 927°C

   
   
   

   4. -123°C

   
   
   

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   NA

   Correct Option: C

   NA

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180. If the pressure amplitude of a sound wave is tripled, then the intensity of the wave increased by a factor

1. 1. 3

   
   
   

   2. 6

   
   
   

   3. 9

   
   
   

   4. √3
      

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   NA

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