A train standing at the outer signal of a railway station blows a whistle of frequency 400 Hz in still air.
1. What is the frequency of the whistle for a platform observer when the train approaches the platform with a speed of 10 m/s
(a) 300 Hz
(b) 412.12 Hz
(c) 350 Hz
(d) 360.50 Hz
2. What is the frequency of the whistle for a platform observer when the train recedes from the platform with a speed of 10 m/s ?
(a) 400.60 Hz
(b) 528.75 Hz
(c) 574.65 Hz
(d) none of these
3. What is the frequency of sound in each case ?
(a) 340 Hz
(b) 350 Hz
(c) 360 Hz
(d) 370 Hz