Question

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)

• A. 600 cps
• B. 660 cps
• C. 990 cps
• D. 330 cps

Answer 1

Answer: (B)

660 cps

Answer 2

$n' = n\left( \frac{v}{v - v_{S}} \right) = 600\left( \frac{330}{300} \right) = 660cps$