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 (if the sound velocity in air is 300 m/s) [CBSE PMT 1998; AIIMS 2000]

• A.            \[{{n}_{1}}=10\,n\]            
• B.            \[{{n}_{1}}=0\]
• C.            \[{{n}_{1}}=0.1\,n\]          
• D.            \[{{n}_{1}}=-0.1\,n\]