A train moves towards a stationary observer with speed 34 m s - 1 . The train blows whistle and its frequency is registered by the observer as ν 1 . If the train's speed is reduced to 17 m s - 1 , then the frequency registered is ν 2 . If the speed of sound is 340 m s - 1 , then the ratio ν 1 ν 2 is

Step-by-step solution

According to Doppler's effect, the approximate frequency heard by the stationary observer, ν = C C - v s ν 0 Case (I) v s = 34   m   s - 1 , where C = Speed of sound in air, v s = Speed of source, and ν 0 = frequency of the source. ∴    ν 1 = 340 340 - 34 ν 0 = 340 306 ν 0                     . . . . i Case (ii) v s = 17   m   s - 1 ∴       ν 2 = 340 340 - 17 ν 0 = 3