161. When a source of sound is in motion towards a stationary observer, the effect observed is

1. 1. Increase in the velocity of sound only

   
   
   

   2. Decrease in the velocity of sound only

   
   
   

   3. Increase in frequency of sound only

   
   
   

   4. Increase in both the velocity and the frequency sound

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   NA

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162. Two waves are given by y₁ = a sin (ωt - kx ) and y₂ = a cos (ωt - kx). The phase difference between them is

1. 1. π / 4

   
   
   

   2. π / 6

   
   
   

   3. π / 8

   
   
   

   4. π / 2

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

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163. Doppler shift in frequency does not depend upon

1. 1. The actual frequency of the wave

   
   
   

   2. The distance of the source from the listener

   
   
   

   3. The velocity of the source

   
   
   

   4. The velocity of the observer

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: B

   NA

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164. If the density of oxygen is 16 times that of hydrogen, what will be the ratio of the velocities of sound in them ?

1. 1. 1 : 4

   
   
   

   2. 4 : 1

   
   
   

   3. 2 : 1

   
   
   

   4. 1 : 16

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: A

   NA

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165. Which one of the following types of glass can cut of ultraviolet rays ?

1. 1. Soda glass

   
   
   

   2. Pyrex glass

   
   
   

   3. Jena glass

   
   
   

   4. Crookes glass

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

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