The equation of a travelling wave is \[y=60\cos (1800t-6x)\] where y is in microns, t in seconds and x in metres. The ratio of maximum particle velocity to velocity of wave propagation is [CBSE PMT 1997; JIPMER 2001, 02]

• A.            \[3.6\times {{10}^{-11}}\]      
• B.            \[3.6\times {{10}^{-6}}\]
• C.            \[3.6\times {{10}^{-4}}\] 
• D.            3.6