All India Engineering / Architecture Entrance Examination (AIEEE)

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AIEEE 2009 Physics

Q.1. Three sound waves of equal amplitudes have frequencies (v – 1), v, (v + 1). They superpose to give beats. The number of beats produced per second will be:

1.  1
   
   
2. 4
   
   
3. 3
   
   
4. 2

Sol: Variation of intensity due to superposition of waves having frequencies v -1 & v and v & v + 1 is as shown

Variation of intensity due to superposition of waves having frequencies v – 1 and v + 1 is as shown

Resultant of (a) and (b) be as shown So number of beats/s = 2

Answer: (4)

 Q.2. The height at which the acceleration due to gravity becomes  (where g = the acceleration due to gravity on the surface of the earth) in terms of R, the radius of the earth is:

1. 
   
   
2. 2R
   
   
3. 
   
   
4. R/2

Sol:    

Answer: (2)