The Total solution for NCERT class 6-12
(i)┬а(a)Frequency of the whistle, ╬╜ = 400 Hz
Speed of the train,┬аvT= 10m/s
Speed of sound,┬аv┬а= 340 m/s
The apparent frequency┬аof the whistle as the trainapproaches the platform is given by the relation:
(b) The apparent frequency┬аof the whistle as the trainrecedes from the platform is given by the relation:
(ii)┬аThe apparent change in the frequency of sound is caused bythe relative motions of the source and the observer. These relative motionsproduce no effect on the speed of sound. Therefore, the speed of sound in airin both the cases remains the same, i.e., 340 m/s.