question_answer

A vehicle, with a horn of frequency n is moving with a velocity of 30 m/s in a direction perpendicular to the straight line joining the observer and the vehicle. The observer perceives the sound to have a frequency \[n+{{n}_{1}}.\] Then \[{{n}_{1}}\] is equal to (if the sound velocity in air is 300 m/s):

A)  \[{{n}_{1}}=10\,n\]        

B)         \[{{n}_{1}}=0\]

C)  \[{{n}_{1}}=0.1\,n\]      

D)         \[{{n}_{1}}=n\]