The frequency of a whistle of an engine is 600 cycles/sec is moving with the speed of 30 m/sec towards an observer. The apparent frequency will be (velocity of sound = 330 m/s) [MP PMT 1989]

(1) 600 cps

(2) 660 cps

(3) 990 cps

(4) 330 cps

(2) n'=nvvvS=600330300=660 cps

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